See: Zeno Clash
Source was licensed or whatever.
You cannot modify the engine in any way whatsoever. It lets you use the engine, but you cannot see how it works or change it.
Listen to this man, he knows what he's talking about.
Basically what I'm wondering is why Source and Unreal's SDKs are free when Torque 3D is $1,000. I know Torque 3D can be used to design games from the ground up, but if you know LUA, Blender, Hammer, Source SDK's choreography tool/face animator, and all the free software used for game design, couldn't you make a game comparable to HL2 from the ground up using free software?
Many things:
With T3D(The $1000 package anyways), you have access to the source code.
With T3D( the less expensive package included this time), you can sell your works, players can run them without a source engine game, etc.
When you make a Source Mod, you have no access to the source code unless you strike a deal with Valve, you can't sell your works unless you do the aforementioned striking of a deal, and players need a source-engine game.
This is avoiding feature lists, also.