Code-named Project: V13, the title is being co-developed by Masthead, which has contributed "proprietary tools and MMOG technology" originally designed for its own post-apocalyptic MMO, Earthrise. In today's announcement, it was noted that "development [of V13] continues under Interplay's direction and control."
Interplay has long planned to develop an MMO set in the post-apocalyptic Fallout universe, going so far as to license the Fallout MMO rights after it sold the property to Fallout 3 maker Bethesda in 2007. But while the V13 code-name is a clear reference to the series and pieces of V13 concept art contain elements of the Fallout universe (such as Nuka-Cola), Interplay has never publicly confirmed if V13 and its Fallout MMO are one and the same--something that will likely prove to be key in the ongoing court battle with Bethesda over the status of certain Fallout rights, including the MMO.
Stated Interplay CEO Herve Caen in today's announcement: "Masthead's technology is impressive and perfect for our Project: V13...This MMOG will have many unique features that we will disclose before launch of the public Beta in 2012."