Both of these companies have made huge mistakes and are acting really childish. This all goes back to original contract(s) where Interplay sold their IP, but Bethesda was so anxious to get a hold of the Fallout IP they bought it with a huge loophole. That was big mistake #1. Bethesda made a huge assumption that Interplay would never be able to meet the stipulations. Since then, Interplay has done everything in their power to manipulate that loophole and stick up a middle finger to Bethesda. Like Rick James, Interplay is "a habitual line stepper." They have sold old games while tying them to Fallout 3, and ignored the contract requiring approval from Bethesda for how they sell their old games. Again, just horrible contract writing on Bethesda's part. They should have bought the old games, instead they make stipulations about how they can be sold. Yet Interplay should realize they need to get some approval from Bethesda, and from the sounds of it they simply ignored any communication with Bethesda.
Next, Interplay has proceeded with the MMO (in a very half assed manner), but from the sounds of it, have done everything they can to screw with the canon created by Bethesda. Instead of working within that framework and even working with Bethesda, they just went off on their own and did what they felt like. So now Bethesda is questioning all use of the Fallout IP outside of the name. Which of course begs the question, how do you allow a company to make a Fallout game and deny them everything about Fallout? This is the stuff the courts are wrestling with. What exactly did the contract allow Interplay to use? I think Bethesda is going too far in stating Interplay can only use the name, but Interplay keeps poking the dragon. Interplay could have probably avoided much of this by working with Bethesda. Bethesda could have avoided this by actually buying all the IP without such big loopholes. Now both are stubborn and they have to battle it out in court in order to figure out what exactly the first contract actually stipulated.
Yes, Bethesda is acting like a bully. Yet Interplay is also acting like a little child by doing everything in their power to screw with Bethesda and manipulate the contract as much as they can. Essentially, they sold their IP, got the cash, and now are acting like they never sold anything.
In the end, the original contracts were simply horrible, and the actions of both companies have made it worse. This will have to be decided in the courts, and one company will look like a huge fool.