What is your time worth? Generally startups seem to have a fairly common lifecycle (at least in the embryonic stages). Vision -> work to prototype/proof of concept -> { Seed | Exit }. If it is not self-funded the founders should have talked to at least Angel investors, they should have a list of questions that investors have been asking them prior to deciding to invest, and they should have a plan for answering those questions. If they don't, then they may have lost their way. If they are lost then staying is a waste of your time.