KDE is a big project, and has lots of apps where you can learn from. You can find small apps, big apps, libraries, WM, nearly everything in that project. It's well documented, easy to code thanks to Qt. You can start from the bottom with small tutorials, and move up in the chain when your experience improves.

You could try Code::Blocks http://www.codeblocks.org/

well, they need a lot of money since all console manufactures loss money on consoles, that's why they also sell games. And they will need an inhouse or very close game publishing company, and a lot of power for a low price to compete.