For software applications like games, does this mean software companies have a lot of extra coding to maintain 3 branches of certain libraries?
I know this is hard to say, but for game development in general, are there specific areas in the software where they will have to write 3 times in order to work in all 3 flavors of windows?
I’m guessing the core software will be untouched, but maybe some drivers will need to be version specific?
It depends how close to the OS you are. If you’re just using the .NET framework or DirectX, probably not much changes between operating systems. If you’re writing drivers or relying on the Win32 API then there definitely could be subtle or not so subtle changes.