Valve adds "all the Team Fortress 2 client and server game code" to its Source mod tools, letting modders "build completely new games based on TF2" and publish them on Steam
"We're already preparing for the porting efforts and a potential Steam release now that we've been legally enabled to pursue that," according to one mod dev
Goddamn, I miss those days! Got a real graphics card for TF2 (edit: I meant TF Classic) so I could see through water. Rocket jumping and cluster bombs, ahhhh. There was a mod with a grappling hook that was amazing.