I've been getting pretty heavily into Mongoose Traveller lately, which also makes great use of the
OGL. Combined with Marc Miller's various (and all very generous) licensing and fan use policies, I am absolutely struck by how vastly superior this all is
as a business model to what
WotC is doing.
Not to mention how much better this is for me as consumer.
There are a ton of free Traveller resources on the web, but instead of reducing my buying of Traveller material, all of these ancillary services are actually increasing it. They are creating and reinforcing my buying patterns.
The same thing happened during the d20 era: for close to 10 years I hardly even looked at another game system outside of the d20 family. Cool
3PP books increased the perceived value of my D&D investment, which led me to buy more
WotC books, miniatures, and other accessories. The
SRD, freely available on the web, made it incredibly easy to prepare adventures and work on my campaign -- which again increased the value of the game.
I'm not talking about hippy-frippy "open source will save the world, man" pie-in-the-sky dreams. I'm talking about the
OGL driving significant, real sales patterns.
I didn't jump on the Mongoose Traveller bandwagon because it used the
OGL. I jumped on because it got good reviews and Traveller has always been on my gamer lifelist. But once I got on, the use of the
OGL coupled with Marc Miller's generosity with his IP are significantly helping to keep me on. (The fact that MGT is an elegant little system is key, too.)