I want to use certain parts of the Game State Management Example in a game I'm making, but I'm not sure how to do this legally. It says in the license that I'm supposed to include a copy of the license with it. So if I make a Visual Studio Solution, I just add the license.txt to the solution? Also, if I use a class and change it, do I have to keep the license info at the top or add that I changed it or what?
I am not a lawyer.
3.D says that a distribution of the source code must include the license; if you don't distribute the source code, you don't need to worry about that sentence. 3.C says that you may not remove any of the notices it mentions, if they are present. That would include a message printed on the screen or a credits dialog.
If you change one of the source classes, I would keep the license info at the top; you don't need to add that you changed it, but it might be a nice thing to add a note saying so.
In general, this is a pretty standard-looking open-ish source license that does a few things to cover the contributors' asses but doesn't require you to do much to comply with it.