Comment by theptip

Meta seems to place a pretty high premium on controlling its open source projects, especially dev tooling. I guess dating back at least to the git maintainers telling them they were doing things wrong with their monorepo and refusing to upstream scale fixes, which precipitated their migration to mercurial (who were more than happy to take the contributions).

Given the change velocity of internal tooling you can understand why owning your own project makes sense here.