Interplay does not have the rights anymore. They actually had some kind of deal with Bethesda back when Interplay were in dire straits that allowed them to make

Interplay does not have the rights anymore. They actually had some kind of deal with Bethesda back when Interplay were in dire straits that allowed them to make a Fallout MMO type of experience after selling the Fallout IP for a couple million dollars to Bethesda. However, they had to do it on a rather compressed schedule, which they naturally didn't meet on their end. Therefore, they lost everything post 2009. Interplay also did a Fallout classics retail release which included Fallout, Fallout 2, and Fallout Tactics. But Bethesda told them they no longer had the rights and Interplay had to get it pulled off store shelves. This was also around 2009 or thereabouts.