Core3 is the working name for the open-source server code. It is the codebase that the SWGEmu developers are constantly working on, and is avaialable for anyone to review, download, and compile.
TC:Nova is the new name of the SWGEmu Test Center Physical Server. Nova works off of Core3. Nove is a testing environment, on which many up and down times, crashes, and tests occur. Players will also notice features such as @ commands (@spice) and Gungan/Jawa Traders, to increase the effectiveness of testing.
TC:Suncrusher will be the 1.0 Release playable "Live" SWGEmu Physical Server. Nova also will works off of Core3. Suncrusher will NOT have any player @ commands, Traders, or shortcuts. It will be for all intents and purposes, the game as it should be.