Open Software License
AuthorLawrence Rosen
Latest version3.0
Publisher2005, Lawrence Rosen
SPDX identifierOSL-1.0, OSL-1.1, OSL-2.0, OSL-2.1, OSL-3.0
FSF approvedYes[1]
OSI approvedYes
GPL compatibleNo[1]
CopyleftYes Edit this on Wikidata

The Open Software License (OSL)[2] is a software license created by Lawrence Rosen. The Open Source Initiative (OSI) has certified it as an open-source license, but the Debian project judged version 1.1[3][4] to be incompatible with the DFSG. The OSL is a copyleft license, with a termination clause triggered by filing a lawsuit alleging patent infringement.

Many people in the free software / open-source community feel that software patents are harmful to software, and are particularly harmful to open-source software.[5] The OSL attempts to counteract that by creating a pool of software which a user can use if that user does not harm it by attacking it with a patent lawsuit.

Key features

Patent action termination clause

The OSL has a termination clause intended to dissuade users from filing patent infringement lawsuits:

10) Termination for Patent Action. This License shall terminate automatically and You may no longer exercise any of the rights granted to You by this License as of the date You commence an action, including a cross-claim or counterclaim, against Licensor or any licensee alleging that the Original Work infringes a patent. This termination provision shall not apply for an action alleging patent infringement by combinations of the Original Work with other software or hardware.[6]

Warranty of provenance

Another goal of the OSL is to warrant provenance.[7]

7) Warranty of Provenance and Disclaimer of Warranty. Licensor warrants that the copyright in and to the Original Work and the patent rights granted herein by Licensor are owned by the Licensor or are sublicensed to You under the terms of this License with the permission of the contributor(s) of those copyrights and patent rights.[6]

Network deployment is distribution

OSL explicitly states that its provisions cover derivative works even when they are distributed only through online applications:

5) External Deployment. The term "External Deployment" means the use, distribution, or communication of the Original Work or Derivative Works in any way such that the Original Work or Derivative Works may be used by anyone other than You, whether those works are distributed or communicated to those persons or made available as an application intended for use over a network. As an express condition for the grants of license hereunder, You must treat any External Deployment by You of the Original Work or a Derivative Work as a distribution under section 1(c).[6]

Comparison with the LGPL/GPL

The OSL is intended to be similar to the LGPL.[8] Note that the definition of Derivative Works in the OSL does not cover linking to OSL software/libraries so software that merely links to OSL software is not subject to the OSL license.

The OSL is not compatible with the GPL.[9] It has been claimed that the OSL is intended to be legally stronger than the GPL (with the main difference "making the software available for use over the Internet requires making the source code available"[10] that is the same goal as the even newer Affero General Public License (AGPL), that is compatible with GPLv3),[10] however, unlike the GPL, the OSL has never been tested in court and is not widely used.

Assent to license

The restriction contained in Section 9 of the OSL reads:

If You distribute or communicate copies of the Original Work or a Derivative Work, You must make a reasonable effort under the circumstances to obtain the express assent of recipients to the terms of this License.[6]

In its analysis of the OSL the Free Software Foundation claims that "this requirement means that distributing OSL software on ordinary FTP sites, sending patches to ordinary mailing lists, or storing the software in an ordinary version control system, can arguably be a violation of the license and would subject violators to possible termination of the license. Thus, the OSL makes it challenging to develop software using the ordinary tools of Free Software development."[1]


If the FSF claim is true then the main difference between the GPL and OSL concerns possible restrictions on redistribution. Both licenses impose a kind of reciprocity condition requiring authors of extensions to the software to license those extensions with the respective license of the original work.

Patent action termination clause

The patent action termination clause, described above, is a further significant difference between the OSL and GPL.

Further provisions

Later versions

It is optional, though common for the copyright holder to add “or any later version” to the distribution terms in order to allow distribution under future versions of the license. This term is not directly mentioned in the OSL. However, it would seem to violate section 16, which requires a verbatim copy of the license.

Open software that uses the OSL

Open software that used the OSL

See also


  1. ^ a b c "Various Licenses and Comments about Them – GNU Project – Free Software Foundation (FSF)". Retrieved March 4, 2012.
  2. ^ "Open Source Initiative OSI – The Open Software License 3.0 (OSL-3.0:Licensing | Open Source Initiative". Retrieved March 4, 2012.
  3. ^ "DFSGLicenses – Debian Wiki". February 28, 2012. Retrieved March 4, 2012.
  4. ^ "Open Source Initiative OSI - The "Open Software License":Licensing". May 1, 2006. Archived from the original on May 1, 2006. Retrieved October 15, 2012.
  5. ^ "BusinessWeek". February 6, 2006. Retrieved March 4, 2012.
  6. ^ a b c d "The Open Software License 3.0 (OSL-3.0)". Open Source Initiative. Retrieved April 21, 2021.
    Text was copied from this source, which is available under a Creative Commons Attribution 4.0 International License.
  7. ^ "LinuxElectrons - Apache Software Foundation Position Regarding Sender ID". October 31, 2005. Archived from the original on October 31, 2005. Retrieved October 15, 2012.
  8. ^ "Open Software License ("OSL") v. 3.0" (PDF). Retrieved October 15, 2012.
  9. ^ "Philosophy of the GNU Project – GNU Project – Free Software Foundation (FSF)". February 26, 2012. Retrieved March 4, 2012.
  10. ^ a b "Choosing an Open Source License". Retrieved March 4, 2012.