Throughout this chapter and book, a variety of helpful SDKs have been recommended to make the game developer's life easier in the process of making games. ClanLib, OGRE, Lua, Python, OpenGL, OpenAL, and so on are all examples of free, open-source software. Even though they are free, each SDK may be distributed under a different license and this may carry with it various terms or implications for the developer. Therefore, readers might find it useful to see a list of all the different open-source licenses and their terms. These can be found at http://www.opensource.org/licenses/.