Oak is an open-source project, and we welcome contributions from all interested collaborators, inside of Google and out.
Oak's current source-of-truth is an internally-hosted git respository that uses Gerrit for code review.
The internal repository is mirrored almost instantly to our public GitHub repository.
Our main development flow is through our internal Gerrit instance, and it's not currently possible to submit changes through the GitHub interface.
However, we still welcome changes from the greater community, and are open to reviewing pull requests from contributors outside of Google. While we can't submit your change directly through the GitHub interface, someone from the Oak team can work with you to make sure that your change gets submitted, with proper attribution.
If you're interested, just open a pull request!
If you are a Googler, see: go/contributing-to-oak