Um, you're assuming that mailing lists serving open source projects
will either (a) knuckle under to the demands of DMARC, or (b) be
willing to inflict the pain caused by DMARC-workarounds on their
users, aren't you?
Yes, those are the only choices at this point.
I can think of one major open source project (namely, the Linux
kernel) which has refused to do either.
I'm reasonably sure you're mistaken here. Don't they rewrite From:
headers?
R's,
John