When Fallout 3 developer Bethesda Softworks purchased the Fallout property from Interplay in April 2007, Interplay retained the right to make a Fallout MMO--on condition it raise at least $30 million in funding and enter scale development within 2 years.
Bethesda evidently does not believe Interplay has met these conditions, as the "Legal Proceedings" section of Interplay's Securities and Exchange Commission report shows:
Interplay recently received notice that Bethesda Softworks, LLC ("Bethesda") intends to terminate the trademark license agreement between Bethesda and Interplay which was entered into April 4, 2007 for the development of FALLOUT MMOG. Despite the fact that no formal action is currently pending, Bethesda claims that Interplay is in breach of the trademark license agreement for failure to commence fill scale development of same by April 4, 2009 and to secure certain funding for the MMOG. Interplay adamantly disputes these claims. Although the potential damages are currently unknown, if Bethesda ultimately prevails and cancels the trademark license agreement, Interplay would lose its license back of the "Fallout" MMOG and any damages resulting therefrom are unknown at this time.
Interplay has released sporadic tidbits on the development of Project V13--the project almost certainly its Fallout MMO--including the hiring of Fallout lead designer Chris Taylor last year, and a recent development partnership with Masthead Studios.
While no formal action is currently pending, should Bethesda follow through and succeed, Interplay will be unable to create a Fallout MMO. It is unknown whether Project V13 would be outright junked or if it could be salvaged under a new property.