Making Sure An Open Source RPG Stays Available
Updated: You can ignore this now. Instead you want to go over to the DominionRules.org website where they are hard at work on v3.0 of the rules.
A long time ago (back when GameDev.net was still new) I interviewed the developers at a site called Dominion Games. They had developed a set of rules for a fantasy role-playing game called, naturally enough, Dominion Rules. They put an open source license on it and encouraged others to write more rules, expansions, character sheets, etc. Keep in mind this was even before Wizards was considering using the D20 license to open up parts of D&D.
Everything was on their website for free as downloadable PDF files. But, there's a problem, they went away. The site is gone and when someone asked me about downloading the rules recently, neither of us could find anyone with a copy. He expanded his search based on some suggestions I made and eventually tracked down copies of a few of the rule books. Here they are from my site so they won't go missing again: The Dominion Rules Digest (the core rules for Dominion Rules 2.0), The Armoury (also for Rules 2.0), and The Spell Books (1.0 version, I don't know if there was ever a 2.0 version)