I own the web app, and need to make sure the code is backed up

Hi, for your purpose, you can use a shared CodeCommit repository: see https://aws.amazon.com/codecommit/features/

Collaboration
AWS CodeCommit is designed for collaborative software development. You can easily commit, 
branch, and merge your code allowing you to easily maintain control of your team’s projects. 
CodeCommit also supports pull requests, which provide a mechanism to request code reviews 
and discuss code with collaborators. You can create a repository from the AWS Management Console, 
AWS CLI, or AWS SDKs and start working with the repository using Git.

This way, all folks needing access to application code can do it.

Best,

Didier