[remram]

I wonder if this could be solved with license terms.

Popular, OSI-approved licenses include clauses like "Neither the name of the <copyright holder> nor the names of its contributors may be used to endorse or promote products derived from this software" (BSD) or restrictions on the use of the original name (see Firefox/Iceweasel drama).

If you put in a clause like "You may not keep the software's name or support URL unless distributing an officially-released version", perhaps it would still be open-source as per OSI, and address those distribution issues? It's easy enough for distributors to patch in their own support mailing-list...

[hedora]

I think you could just assert that unmerged PR's have the following license:

"All Rights Reserved"

[remram]

This won't work with most licenses, if you don't own copyright over the totality of trunk. The PR is definitely a derivative of the trunk...