+1 to not proactively changing anything. I really doubt there will be any negative issues so barring a compelling feature of a new platform seems like it'd be a bunch of work for no net gain.
What we should do though is have an alternate official git repo mirroring the primary pgjdbc repo. Everyone's local copy is essentially a backup as well but this would cover having a central agreed upon master to use as the base if we ever lost the primary on GitHub.
Looks like there's already an empty pgjdbc.git on the git.postgresql.org server (says the owner is Dave too!) so that seems the logical destination for this. Any chance we can set it up to mirror master from the GitHub repo? We never rewrite history on master so it could be purely additive mirror that rejects historical rewrites (i.e. can't be corrupted externally).