Well, considering the ide is qt-based it's probably not that hard to port it to Linux.
Edit: Actually, is the ide even in the repository? I've yet to find it if it is.
When you ask for the IDE do you then mean the environment to script in? In that case you will need Torsion, codeweaver or notepad++, or something like it(hence not a part of Torque). If you mean IDE for the source codes then it is Visual Studio 2010 or similar for other systems than windows(hence also a third part software).
If you mean the source code IDE for the world editor(like the GUI system), then it should be under engine-source-gui as far as I remember.
The toolbox seems to be in closed qt.dll files(if I am not mistaken). Also under the file called engine you can find all the codes for pretty much everything(including gui).
Sorry if I am a little unclear here but I do not really understand what you want to find(which IDE do you want to find?).
Best,
Update: I found this link, perhaps that clears things up:
http://garagegames.com/community/forums/viewthread/131742