jj is a "unofficial" Google project that one has to sign a Google CLA to contribute to. I don't think it would be a good idea to trust/transition to a system like that from git.
It's always the first step. The second step would be switching the license and only supporting the changed licensed version, then "donating" the unmaintained version to the community.
Has Google ever done this before though? I'm not much of a fan of Google either, but they tend to just abandon products outright rather than relicence them.