I don't know whether that counts as arms-length usage (is it "effectively two parts of one program"?) -- that may be a question for the lawyers.
But I can tell you this much: if you decide to simplify everything by just licensing your application with a GPLv3-compatible license and release the source,
that does not in any way obligate you to listen to or accept other peoples' input, contributions, pull requests, etc.
(You are free to ignore them or listen to them, as you please.)
The GPL protects peoples' right to know what your application does, and modify their own personal copies if they want to.
If they want
you to listen to them, too, they can take out a support contract.
