Just to be clear:
Volition = Game Engine
Interplay = IP
THQ = Multiplayer Code
Am I correct with this information?
Not quite. THQ (which, just to be clear, doesn't exist anymore) never owned any part of FreeSpace; it was always and only an Interplay property.
A brief reminder on how game IP licensing usually works: A developer has an idea. They talk to a publisher about it. The publisher agrees to fund development. In return for those funds, the publisher gets the rights to the franchise; if the game is a success, then the publisher will commission a sequel (usually from the original developers).
In the case of FreeSpace, the IP is owned by Interplay. Volition owned the engine, which allowed them to give us the source code, but when they left Interplay for THQ, their ability to make more FreeSpace was seriously diminished.
When developing the engine, Volition made use of some technologies Interplay owned (PXO matchmaking and MVE cutscene playback), which had to be removed from the source code but which were later reimplemented by SCP.