I am a fan of GURPS and while talking about GURPS Dungeon Fantasy a couple of folks mentioned they would feel more comfortable using Blackmarsh for a fan publication if it was dual licensed under a Creative Commons License.
So I did just that, the Blackmarsh Setting Reference Document is now dual licensed under CC BY-NC-SA. You can download the SRD, or use RPGNow.
When you create a fan publication you can choose either license to use. The Creative Common license should make it either to release a Blackmarsh related fan publication for a RPG that doesn't have an open license. Please check the Game Publisher's policy on fan publications first.