In the past, many open-source games have been released while they are still in a mainly-alpha stage. This detracts from the playability of the game as people get annoyed by bugs or incomplete content (examples include Planeshift and Eternal Lands) that quickly get annoying and get a reputation amongst gamers as incomplete or buggy games. Sometimes people even begin to believe that open-source games in general are incomplete and buggy. This is not the case, as shown by games like Battle for Wesnoth and Assault Cube which are, as far as I can tell, mostly bug-free and completely playable.

So I propose a new style of open-source game development. Any part of the games (source, content, executables) should be kept somewhat restricted until the game is at least in an alpha state. At this point some screenshots should be put out, maybe a test level, but not actually released to the public. Once the game gets to a beta stage, put out an announcement for beta testers. There are many open-source gamers out there who would love to help you out.

Problems:

• Goes against GNU freedom. Many open-source people would have a problem with this. Solution? Don't follow it if you don't want to. It is up to the game developer to decide whether they want to release the game under the GPL/Creative Commons/etc. The GNU and its supporters should not be stuffing their opinions down other peoples' throats.
• Long development times. Having the game unreleased would mean that less people would jump on the bandwagon to help it out. Solution? Talk about the game. Put up a website/blog/wiki talking about the game and let people tell you that they are interested in helping out. If they ask for the content, you can give it to them. There is a big difference between giving the content on request and making it available for download on your page (that difference being people who don't really care about it won't try it until it's actually something playable).

This is not a license, it is not a defined pattern of doing things, it is just a suggestion to those who are interested. Follow it or not, this is just my solution to the problem of people getting bored with open-source games.