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A: This is potentially possible, but there are caveats which mean it might not be the best solution in the end. Please see: Notes On Github Organizations
Q: Can I use my existing Github account or do I have to create a new one?
A: You can do either. Github handles SSO slightly differently than other platforms, and you’ll basically need to auth a second time to access any resources that belong to an organization. This means that you can use a pre-existing Github account (and that all of your personal repos will stay as-is) or create a new one if you’d like to keep things absolutely separate. Either way, organization members will not be able to access your personal repos unless they are already set to public visibility or you give them access via another means.