NO, main dev of !mustard clarified 10 days ago that there's no #pumpio support http://ur1.ca/e34ik
Well, @macno actually says he wishes to support !pumpio in #Mustard but can't do it in the near future b/c of lack of time.
@erkanyilmaz Altho #mustard won't work w/ pump.io (maybe later) !mustard will continue to work with !StatusNet #federati instances, correct?