The Source SDK is a software development kit compiled by Valve Software that is used to create maps or mods for the Source engine, with the exception of Left 4 Dead, Left 4 Dead 2, and Alien Swarm. These games are packaged with their own SDKs, called the Left 4 Dead Authoring...

Source SDK is the most popular Windows & Mac alternative to UnrealEd.
Source SDK is the most popular commercial alternative to UnrealEd.
- Source SDK is Paid and Proprietary


