He came back in the Magneto: Not A Hero mini. Astra resurrected him to pose as Our Lord Magneto at a mutant rally. She had a whole troop of cloned BOEM members. Joseph tried to temp Our Lord back into the villainy game, but he refused. Most of the clones were killed, but Astra and Joseph were locked up in the X-Brig until the sinking of Utopia. Danger freed all of the criminals rather than let them die.
Astra's another obscure one. She's sort of like the original BOEM's Voyager in that she was retconned in as a member, supposedly working behind the scenes during all of that 1960s stuff, but never seen until 1999.
Those retconned-in founding members are the worst.