OGF meaning in Community ?

Open gaming is a movement within the tabletop role-playing game (RPG) industry with superficial similarities to the open source software movement. The key aspect is that copyright holders license their works under public copyright licenses that permit others to make copies or create derivative works of the game.

A number of role-playing game publishers have joined the open gaming movement, largely as a result of the release of the original System Reference Document (SRD) by Wizards of the Coast, which consisted of the core rules of Dungeons & Dragons 3rd edition. Open gaming has also been popular among small press role-playing game and supplement authors.