Open-source software is not always freeware

I read a comment from a Humble Bundle purchaser who was confused when we made the open-source announcement, saying he hadn't known that the games were about to become freeware. However, the games are not freeware, they are still for sale at their usual price. Open-source software and freeware are not the same thing! Here is a Venn diagram showing their relationship:

Most open-source software (OSS) is freeware, but it doesn't have to be. Here are a few examples of open-source games which are not free:

• Battle For Wesnoth is an open-source game that is free for computers, but is for sale on the App Store.
• Sleep Is Death is released into the public domain (source code, data, and all), but the developer charges a price to download it.
• Quake 1-3 are all open-source under the GPL, but the data is not, so users need a licensed copy in order to actually play the game.
• Marathon and its sequels are all open-source and free on personal computers, but not on consoles.

With Lugaru, the source code and data are both in the repository, but I'm not really worried about it cannibalizing sales. The source code is intended to help out modders and aspiring game programmers, and will probably not be particularly useful for gamers who just want to get the game for free. Since we have no DRM, there are probably easier ways to pirate the game than learning how to compile and run a C++ project from a Mercurial repo.

Many game developers would enjoy the benefits of open-source software, such as helping out other programmers and getting more eyes to help find bugs, but they also have to make a living by selling their games. Can you think of any ways to combine these two goals?