On GitHub, users (mainly software engineers) can indicate if they are hireable or not.

Hireable means open to job offers. When candidates have a hireable label included on their profiles they have indicated at some point on GitHub that they are open to job opportunities.

Do take into account that this can be an outdated status of the candidate (in case the candidate has put that on their profile a while ago and forgot to change it).

You can however use this information in deciding if it's worthwhile to reach out to the candidate.