On what grounds would GOG do that? They don't own the IPs of the games they sell (except for the IPs for CD Projekt Red games that their sister company owns).
Therefore, they seem to have no basis on which they could fight back legally.
But they have contracts with the publishers, no?
Why would GOG even alienate a potential publisher?
Look at it this way:
Let's say you imported "i'crap" into the country and I bought a large quantity from you to resell them to end customers. Let's also say it was proven (for the sake of this example) that you had stolen those products. Now, you didn't have the right to sell those in the first place....
The result would be that the agreement between you and I were nullified, as a result, my "contracts" to the end customers would also be nullified effective immediately. I could en up in jail, receive a large financial punishment, and the products could be called back.
Interplay is accused of not having paid the lease money to Parallax i.e. the right to sell the games as a WHOLE to others, like GOG. With the petition from Parallax, Interplay no longer had the right to give GOG a resell contract. That contract got invalid and the games were subsequently removed from the catalog. (Well, legally it's in a state of limbo until a court rules either way.)
Now, in the states you can sue everyone over anything, so GOG could sue Interplay for foul play
. However, it would be pointless. Interplay still is a publisher with other games, and even IF GOG had a slightest right to claim anything legally, it would only hurt them.
If GOG bought Parallax and its IPs, then
GOG could put pressure on Interplay into better deals, money and what not. But that's purely fictional and won't happen.
The whole thing is now sadly a proxied mine field.
The team behind Parallax/Overload don't want anything to do with Interplay and the trademarked "Descent". You can imagine why the team behind Overload and the team behind D:U don't collaborate, not to mention they each went their own way. D:U has rented the name from Interplay but it is a DM-mix between Q3+UT+Descent in designed buildings (not hollowed out caves).
With every respect to the creators, they've really made a fun and unique game, I just quite honestly don't think it actually deserves the name. The naming should have been the other way around. Again, just purely fantasy.