5
Currently the osCommerce module does not support shared user data with Xoops. Therefore, your customers will have to register twice if you want them to be registered in your XOOPS site and osCommerce. There has been much debate about this issue, but for now, this is the way it will stay.
No-ah, on the other hand, seems to have a more seemless integration with XOOPS and is actively being developed. If you are new to XOOPS and/or eCommerce, I would recommend to take a look at No-ah.