This proposal has now passed. This adds a new "founder" Relationship Attribute to the Member of Band Relationship Type.

Updated Member of Band Relationship Type wikipage: http://wiki.musicbrainz.org/User:BrianFreud/Member_Of_Band_Relationship_Type_Proposal

When this attribute has been added, besides this ticket, http://bugs.musicbrainz.org/ticket/1009 can also (finally, after 4 years! ) be closed.

I don't recall if Relationship Attributes also need a linked wikipage besides the Relationship Type's page, but in case they do: http://wiki.musicbrainz.org/Founder_Relationship_Attribute