The widely used HL2 mod, Garry's Mod, will now be officially sold via Steam for $10. The newest release will be the initial pay-for release, while the current stable release will remain a free demo. Good for those guys...

"The litmus test of whether or not they do that will be the relative sizes and productivity of the paid and free communities. The two versions will not be compatible, 9.1 being the rewrite it is, and as time goes on the gap between each will grow."