Godoc (pkg.go.dev) doesn't host documentation due to "license restrictions"

https://pkg.go.dev/github.com/apache/beam@v2.29.0+incompatible/sdks/go/pkg/beam renders an error "Documentation not displayed due to license restrictions." It's unclear what the exact complaint is (speculating it could be a transitive dependency?)

This doesn't affect 2.28 & 2.27 (did not check further back)

Further dev@ list context: https://lists.apache.org/thread.html/r2e8347ec85e1ee4778e355a8b2a8c1566a07ad8a843b18e4e42633be%40%3Cdev.beam.apache.org%3E