2D Boy released their prototyping framework on their homepage. It's easy to use, but may not fit the purpose of my game (or your game) very well. Some changes are made to the framework to give it more functionality.
Oh, and to save space, only source files in /Boy and /BoyLib are included.
The original 2D Boy source code doesn't have any license. So this version comes with the simple license of MIT that just says you can basically do anything with it.
These details are provided for information only. No information here is legal advice and should not be used as such.