After I created it, I've found Template:FamilyTree CP/CMS which has very interesting layout. Maybe it is also worth to use here?
Pro: smybols show important relations: "influence only", "major reimplementation of", "improvement", "rebranding".
Pro: columns can be named S/360, S/370, ..., z9 neatly visualising OS generations as opposed to HW generations.
Pro: is horizontal -> is less awkward if included in stub articles
Con: not WP:AS-style compatible.
Con: is horizontal -> should be included on bottom of article -> is less visible -> is less useful.

The layout

--Kubanczyk 14:30, 23 October 2007 (UTC)Reply[reply]

When I added a link to OS/VS2 (SVS), I made two other changes that might require explanation:

• I indented MVS in order to show its relationsip to OS/360 (MVT)

• I deleted MVS/370. IBM coined the term MVS/370 after it announced MVS/XA as a collective noun to refer to everything from OS/VS2 R2 through MVS/SP Version 1, all of which are liasted in the template.

Note: the MVS/370 article is incorrect, and there have been no responses to Talk:MVS/370. Shmuel (Seymour J.) Metz Username:Chatul (talk) 11:58, 8 August 2010 (UTC)Reply[reply]

If the title of the infobox is History of IBM mainframe operating systems then should it not depict the history of IBM mainframe operating systems, rather than just listing those systems for which there is a separate wikipedia article? I believe that VSE/SP should be reinstated. Shmuel (Seymour J.) Metz Username:Chatul (talk) 16:15, 27 October 2010 (UTC)Reply[reply]

This navbox does not list all IBM mainframe operating systems, but only the notable ones. This navbox is to ease navigation, not to clutter the wikipedia. It got out of control and grew to ridiculous size already. I agree about adding VSE/SP, provided there is an article for it at VSE/SP. Otherwise there is not much point in adding it to the navbox, because nobody can navigate to the actual article. --Kubanczyk (talk) 22:11, 27 October 2010 (UTC)Reply[reply]

I'm not sure what you mean by a nav box; neither the text of Template:History of IBM mainframe operating_systems nor the source for the infobox shows such a term. If you were thinking of ((navbox)), that's for linking back to the template.

VSE/SP is notable because it was a bridge between DOS/VSE and VSE/ESA and was the current version for many years.

VSE/SP belongs in DOS/360 and successors; there is no need for a separate article. Do you propose removing entries from the infobox every time someone merges two OS articles? Shmuel (Seymour J.) Metz Username:Chatul (talk) 14:11, 28 October 2010 (UTC)Reply[reply]

I can't see how it improves our encyclopedia; anyway I WP:DGAF. --Kubanczyk (talk) 10:15, 31 October 2010 (UTC)Reply[reply]

Since this box includes non-IBM systems (ORVYL,WYLBUR,UTS), what about Telpar. I believe it most closely esembled DOS. Somewhere I have the source for this, but no documentation. Peter Flass (talk) 19:18, 3 January 2012 (UTC)Reply[reply]

What about ports of *ix systems, e.g., Solaris? Shmuel (Seymour J.) Metz Username:Chatul (talk) 20:06, 5 January 2012 (UTC)Reply[reply]

What about them? They're already in the infobox. Guy Harris (talk) 19:18, 6 February 2012 (UTC)Reply[reply]

I don't think it's appropriate to group TSS with "S/360 and successors." It should have a major heading of its own. Although not widely used it introduced a number of important ideas. Peter Flass (talk) 12:00, 17 October 2013 (UTC)Reply[reply]

I'd go the other way; put all of the S/360 OS lines under "S/360 and successors." BTW, what was the OS for the 9020? Shmuel (Seymour J.) Metz Username:Chatul (talk) 20:42, 18 October 2013 (UTC)Reply[reply]