What happens to a GitHub account and associated repositories when an individual leaves MIT?
Access to the GitHub account remains in place as long as your MIT email address and associated Kerberos account is active. Student accounts are typically deactivated in the January following your graduation date, and staff accounts are typically deactivated at the end of employment.
To preserve access to the information you've created after your MIT email account is deactivated, it's possible to transfer a repository between users or organizations. We suggest that you create a Touchstone collaboration account using an email address to which you'll have access after your MIT email address is gone. Then you can transfer the repository to that address.
Here are the transfer instructions: https://help.github.com/enterprise/2.1/user/articles/transferring-a-repository/
This page of Github information includes links on the steps associated with creating a Touchstone collaboration account: http://kb.mit.edu/confluence/x/iQMrCQ
Alternately, you can transfer the repository to someone else with an MIT email address. Those without either an @mit.edu account or a Touchstone collaboration account cannot see repositories at github.mit.edu.
You can also transfer your repository to a personal GitHub account following these instructions from GitHub.com: https://help.github.com/articles/transferring-a-repository-owned-by-your-organization/