So, Activision killed the auctions. In all fairness, while they don't own Larry, they do own much of the other Sierra franchises, and they share engines.
I imagine the legal issue is referring to the system scripts that the AGI and SCI games all share. There's just one problem, though: many of those scripts are also in freely available demos. I took advantage of that fact when creating the SCI01 template game, using the QFG2 demo as the foundation and the interpreter from the EGA 1990 Christmas Card.
If I had to take a guess, this is one of those scenarios where Activison is compelled to act. You can’t pick and choose when to enforce IP rights. If they chose not to go after Al and then someone else releases source code that they actually care about, attorneys can point to ALS scenario and say Activison is being partial and selective in their enforcement of their IP rights, which you can’t do under US law.
That would be true to an extent with trademarks, but it's completely wrong copyright-wise. A copyright owner
can, in fact, pick and choose when to enforce their rights. The worst thing that would happen by ignoring copyright violations is less damages awarded to the copyright owner in a lawsuit.
I'm no lawyer, by the way; I just read the
TV Tropes article regarding copyright law (it explains that defending a copyright is not
required, simply
allowed), as well as
this article regarding copyright myths (the relevant one is number 5).