This is a good question that hasn't been explicitly answered by DreamHost. Yes, you can set up multiple repositories each with multiple users. Each has its own userlist, so while you can use the same username and password, it won't be the same exact account.
The issue that hasn't been addressed is if it violates the TOS for storing content that's not used for a website. You'd have to contact Sales to find out if there's a problem with this.