For MediaWiki (recent comments | status changes | tags | authors | states | release notes | statistics)
See at http://translatewiki.net/wiki/Special:Version
diff3 diff3 (GNU diffutils) 2.8.1
diff diff (GNU diffutils) 2.8.1
Bug or feature?
translatewiki.net has set:
$wgExternalDiffEngine = 'wikidiff2';
$wgDiff3 = "/usr/bin/diff3";
It's committed for the comment 0 on the bug 14611.
Special:Version should show all third party software which it depends on in Software table, typically graphical engine (eg. ImageMagick), diff engine etc...