You would like to continue using UCSB's Github after you graduate.
Unfortunately, due to the GitHub License stipulated in Can I use GitHub on github.ucsb.edu? and https://github.com/ucsb/github-guide/blob/master/README.md
Any active UCSB student, faculty, or staff that works directly in support of students’ education is eligible for a GitHub account.
They can log in using their UCSBnetID Username and Password to access GitHub.
Please also note that you are creating/using a personal Github account and then linking it to the UCSB Github through single sign in (SSO)
Due to the licensing requirements for GitHub, we can only offer the service to active Student, Faculty or Staff members.
If you are not one of the above, you will need permission from a UCSB Department member under their sponsorship, with them making a guest/affiliate UCSBnetID through the Identity Annex.
It is highly recommended that you transfer your github repos to a personal one prior to leaving.
Once a UCSBnetID account has been deactivated, all access to your UCSB Github repo is terminated.
Please refer to I want to migrate my current repos from github.com to github.ucsb.edu. Is this possible? on migrating your repos.