Original author(s)Novell
Initial releaseMarch 4, 2009; 15 years ago (2009-03-04)
Stable release[1] / 27 April 2011
Preview release
4.0 Preview 1[2] / 15 February 2011
Written inC, C++, C#
Operating systemLinux
TypeWeb Application framework
LicenseLGPL 2 with proprietary codecs

Moonlight is a discontinued free and open source implementation for Linux and other Unix-based operating systems of the Microsoft Silverlight application framework, developed and then abandoned by the Mono Project.[3][4] Like Silverlight, Moonlight was a web application framework which provided capabilities similar to those of Adobe Flash, integrating multimedia, graphics, animations and interactivity into a single runtime environment.

History and overview

Release History
Date Version
2009-02-11 Moonlight 1.0[5]
2009-12-17 Moonlight 2.0[6]
2010-02-03 Moonlight 3.0 Preview 1[7]
2011-02-15 Moonlight 4 Preview 1[8]

In an interview in the beginning of June 2007, Miguel de Icaza said the Mono team expected to offer a "feasibility 'alpha' demo" in mid-June 2007, with support for Mozilla Firefox on Linux by the end of the year.[9]

After a 21-day hacking spree by the Mono team (including Chris Toshok, Larry Ewing and Jeffrey Stedfast among others), a public demo was shown at Microsoft ReMIX conference in Paris, France on June 21, 2007.[10][11][12][13]

However, in September 2007, developers still needed to install and compile a lot of Mono and Olive (the experimental Mono subproject for .NET 3.0 support) modules from the Mono SVN repository to be able to test Moonlight.[14] A Moonlight IDE, named Lunar Eclipse, exists in SVN for XAML designs. Moonlight uses Cairo for rendering.[15]

Moonlight was provided as a plugin for Firefox and Chrome on popular Linux distributions.[16] The plugin itself does not include a media codec pack, but when the Moonlight plugin detects playable media it refers users to download a free Media codec pack from Microsoft.

Moonlight 2.0 tracked the Silverlight 2.0 implementation. The first completed version, Moonlight 1.0, supporting Silverlight 1.0, was released in January 2009. Moonlight 2.0 was released in December 2009.[17] The Moonlight 2.0 release also contained some features of Silverlight 3 including a pluggable media framework which allowed Moonlight to work with pluggable open codecs, such as Theora and Dirac.[18]

Preview releases of Moonlight 4.0, targeting Silverlight 4 compatibility, were released in early 2011.[19]

In April 2011, the Moonlight team demonstrated Moonlight running on Android tablets and phones at the MIX11 Web Developers conference in Las Vegas.[20]

Shortly after the April 2011 release, Attachmate, parent to developer Mono, laid off an undisclosed number of Mono employees,[21] and announced a deal with startup Xamarin for Mono development and support.[22] At that time, Xamarin CEO Nat Friedman affirmed their commitment to the Moonlight project, although there were no outward signs of any further development afterward.

In December 2011, de Icaza announced that work on Moonlight had stopped with no future plans. He explained that Microsoft had "cut the air supply" to it by omitting cross-platform components, making it a web-only plugin, and including Windows-only features. He advised developers to separate user interface code from the rest of their application development to ensure "a great UI experience on every platform (Mac, Linux, Android, iOS, Windows and Web)" without being dependent on third party APIs.[23]


Silverlight supports Digital Rights Management in its multimedia stack, but Microsoft will not license their PlayReady DRM software for the Moonlight project to use and so Moonlight is unable to play encrypted content.[24]

Desktop support

Moonlight was also usable outside of the browser as a Gtk+ widget (known as Moonlight.Gtk). A number of Desklets were written using this new technology during the Novell Hack Week in 2007.[25]

MoonBase is an experimental set of helper classes built on top of Moonlight.Gtk that can be used to create full blown C# desktop applications using the Moonlight (Silverlight 4.0) widgets and XAML files.[26] MoonBase also has a related XAML editor/previewer.[27]

Microsoft support

Shortly after the first demo at MIX 07 in Paris, Microsoft began cooperating with Novell to help with the building of Moonlight.[28] Support included giving exclusive access to Novell for the following Silverlight artifacts:[29]

Microsoft released two public covenants not to sue for the infringement of its patents when using Moonlight. The first one covered Moonlight 1 and 2, is quite restrictive and covered only the use of Moonlight as a plugin in a browser, only implementations that are not GPLv3 licensed, and only if the Moonlight implementation has been obtained from Novell. It also notes that Microsoft may rescind these usage rights.[30]

The second covenant was an updated and broader covenant that no longer limits the covenant to users that obtain Moonlight from Novell, it covers any uses of Moonlight regardless of where it was obtained. The updated covenant covers the implementations as shipped by Novell for versions 3 and 4, it no longer distinguishes Novell from other distributions of Moonlight and expands the covenant to desktop applications created with Moonlight. The covenant does not extend to forks licensed under the GNU GPL (Moonlight itself uses the Lesser GPLv2).[31]

Codecs integration

Although Moonlight is free software, the final version was going to use binary-only audio and video codecs provided by Microsoft which will be licensed for use with Moonlight only when used as a browser plugin (see above). The Windows media pack is not distributed together with the Moonlight plugin but the first time when media content in Silverlight is detected the user will be prompted to download the pack containing the codecs used in Silverlight directly from Microsoft.

Self built versions could still use the FFmpeg library and there was discussion about adding GStreamer support as an alternative to using Microsoft's binary codecs for those who wish to use GStreamer instead and also for use when used outside of a browser.

Mono architect Miguel de Icaza blogged that the Mono team prototyped Moonlight multimedia support using the LGPL-licensed FFmpeg engine but that they were unable to redistribute packaged versions that used that library due to FFmpeg codec licensing issues inside of the United States.[29][32]

Moonlight in other distributions

After the release of Moonlight 2, a covenant provided by Microsoft was updated to ensure that other third party distributors can distribute Moonlight without their users having to worry about getting sued over patent infringement by Microsoft.[33] This covenant can be found on the Microsoft website.

Kevin Kofler and Tom Callaway, of Fedora, have stated publicly that the last covenant was "not acceptable" for that distribution and that "it is still not permissible in Fedora".[34]

The version of Moonlight that was going to be available direct from Novell would have access to licensed closed source media codecs provided free of charge by Microsoft. Third-party distributions of Moonlight would only be able to play non-patent encumbered media like Vorbis, Theora and Ogg. To support other formats, the distributors would have had to choose from a few licensing options:

At the PDC conference on October 13, 2008, Microsoft placed the 'Silverlight XAML Vocabulary' under the Microsoft Open Specification Promise,[35] stating in a press release, "The Silverlight XAML vocabulary specification, released under the Microsoft Open Specification Promise, will better enable third-party ISVs to create products that can read and write XAML for Silverlight." Since Moonlight is essentially a XAML reader, Debian's position is that Moonlight is safe for them to redistribute (leaving each user to agree to their own licensing for Microsoft's and others' binary codecs).[36]

See also


  1. ^ "moon/".
  2. ^ "Moonlight 4 Preview 1 is out".
  3. ^ Miguel de Icaza (May 29, 2012). "Miguel de Icaza on ASP.NET MVC, Moonlight, and the Android Lawsuit". Retrieved 2014-02-06.
  4. ^ Foley, Mary-Jo. "Xamarin abandons its Silverlight for Linux technology". All About Microsoft. ZDNet. Archived from the original on June 1, 2012. Retrieved 1 June 2012.
  5. ^ "Moonlight 1.0 goes live - Miguel de Icaza".
  6. ^ "Releasing Moonlight 2, Roadmap to Moonlight 3 and 4 - Miguel de Icaza".
  7. ^ "Moonlight 3.0 Preview 1 - Miguel de Icaza".
  8. ^ "Moonlight 4 Preview 1 is out - Miguel de Icaza".
  9. ^ Dana Gardner. "the FASTforward blog: Expect a June demo of Silverlight on Linux, sans browser". Archived from the original on 2007-09-28. Retrieved 2007-06-06.
  10. ^ "Implementing Silverlight in 21 Days". Miguel de Icaza. Retrieved 2007-06-22.
  11. ^ "Implementing Silverlight in 21 Days". Jeffrey Stedfast. 21 June 2007. Retrieved 2007-06-21.
  12. ^ "Moonlight". Chris Toshok. Archived from the original on 2007-11-14. Retrieved 2007-06-21.
  13. ^ "Mono Silverlight implementation emerges after epic hackathon". Ars Technica. 22 June 2007. Retrieved 2007-06-22.
  14. ^ "Moonlight: Getting started". Mono Team. Retrieved 2007-09-02.
  15. ^ Moonlight Notes
  16. ^ "Moonlight Supported Platforms". Retrieved 2009-05-17.
  17. ^ "Moonlight 2 is now available". The Silverlight Team blog. 2009-12-17. Archived from the original on 2012-08-23. Retrieved 2009-12-19.
  18. ^ "First Moonlight 2.0 Preview is Out". Miguel de Icaza. Retrieved 2009-05-04. We have developed a handful of open source codecs for Dirac, Vorbis and ADPCM that can be used with Silverlight 3/Moonlight Preview based on existing C# and Java implementations. Hopefully someone will help us fill in the blanks with more codecs (like Theora).
  19. ^ "Moonlight 4 Preview Now Available". The Silverlight Team Blog. 2011-02-15.
  20. ^ "Moonlight on Android". A Moment of Zen. 2011-04-15.
  21. ^ "Attachmate lays off Mono employees". 2011-05-03.
  22. ^ "SUSE Joins Xamarin for Mono". 2011-08-10.
  23. ^ "Moonlight Mailing List". Xamarin. 2011.
  24. ^ "Discussion on official Silverlight forum".
  25. ^ "Moonlight Desklets demo on YouTube". Mono Team. Retrieved 2007-06-25.
  26. ^ MoonBase
  27. ^ XamlPreviewer
  28. ^ Foley, Mary Jo (2007-09-25). "Microsoft officially 'extends support' for Novell's Silverlight Linux port". ZDNet. Archived from the original on September 7, 2007. Retrieved 2007-10-13.
  29. ^ a b de Icaza, Miguel (2007-09-05). "Microsoft/Novell Collaboration on Silverlight". Retrieved 2007-10-13.
  30. ^ "Covenant to Downstream Recipients of Moonlight - Microsoft & Novell Interoperability Collaboration". Microsoft. 2007-09-28. Retrieved 2008-03-08. "Downstream Recipient" means an entity or individual that uses for its intended purpose a Moonlight Implementation obtained directly from Novell or through an Intermediate Recipient... Microsoft reserves the right to update (including discontinue) the foregoing covenant... "Moonlight Implementation" means only those specific portions of Moonlight 1.0 or Moonlight 1.1 that run only as a plug-in to a browser on a Personal Computer and are not licensed under GPLv3 or a Similar License.
  31. ^ "Covenant to End Users of Moonlight 3 and 4". Microsoft. Retrieved 2010-05-11.
  32. ^ Ramji, Sam (2007-09-05). "The Novell-Microsoft Wheeler Dealers Speak". Archived from the original on 2012-05-27. Retrieved 2007-10-13. After a great deal of work between the Moonlight and .NET teams, we're ready to formally announce that we (Microsoft and Novell) will be bringing Silverlight to Linux (Sam Ramji is Director of Microsoft's Open Source Software Lab)
  33. ^ a b Miguel de Icaza (2009-12-17). "Releasing Moonlight 2, Roadmap to Moonlight 3 and 4". Retrieved 2009-12-18.
  34. ^ Tom Callaway (December 23, 2009). "Re: New covenant published". gmane.linux.redhat.fedora.devel. Archived from the original on May 6, 2017. Retrieved 2010-01-11.
  35. ^ "Microsoft Releases Silverlight 2, Already Reaching One in Four Consumers Worldwide". Microsoft. 2008-10-13. Retrieved 2008-10-13.
  36. ^ "Moonlight for Debian". Debian Wiki. Retrieved 28 April 2017. Moonlight 1.0 is essentially a XAML renderer with codec support. All plugin logic is handled by the browser's Javascript engine. XAML is covered by an irrevocable patent grant from Microsoft, as shown here. ((cite web)): External link in |quote= (help)