As of today, Apple is now offering commit access to third parties with a proven contribution track record. The updated policy is as follows:
“If you would like commit access, please send an email to the code owners list with a list of 5 non-trivial pull requests that we accepted without modifications.”
If you want to start contributing to Swift, the team has a set of “starter bugs” you can work on, building up to non-trivial contributions. To learn more about contributing code, visit swift.org’s page that details the process.