I don’t think you will ever find it, cause actually, there is a small problem… 2.25 isn’t GPL’d so they couldn’t possibly release the full sources of it… Also there was the known issue with the 2.25’s Game Engine, which is commercial and thus can’t be included…
I think I explained it enough in my previous post…
The game engine was commercial and most probably patented/copyrighted, so they couldn’t include it’s source, along with Blender sources… That’s why in the following releases, the Game Engine is disabled after all…
I think they released a snippet of the code immediatelly after the end of the funding campaign and the openning of Blender.org… Perhaps this is what you are looking after… I’m not sure if it was 2.25’s sources or based on the sources of a previous release, but in any case the Game engine is not included in there… So the sources are not complete…
Maybe someone else can help you better than I can… I don’t know… Better check with ztonzy’s suggestion…