I've been creating user logins for a particular customer and I see that each user can see and edit all the courses created by other users for that same customer.  "Share Content" is already set to false for all the users.

Is there any way to configure MyUdutu so that a particular user can't see, or at least can't edit, others' courses?

Currently, if you add a user to an account, you effectively give them permission to see and edit all courses in that account.  We'll be expanding role levels down the road, but until then the best way to accomplish what you want would be to create a new account for each group of courses you want multiple individuals to edit, and add those users to the accounts.