No, Meta’s contract has explicit carve-outs for Open-Source work done on personal time that are more generous than Canonical’s (I had to choose between the two 3 months ago).
Meta has its own production fork of CPython, Cinder:
This isn't legal/enforceable in California. Your own work on your own time on your own equipment is your own property. It's messier if you're building a direct competitor or using proprietary knowledge.
