I'm not sure such usage would be permitted on a shared server, but I think you would be allowed to do it on a VPS or a dedicated server. I would email firstname.lastname@example.org to ask them specifics. They would want to know how much data will be stored, and how much traffic is expected (maximum levels). I presume that your clients are maintaining the data (uploading, editing, deleting) themselves (not you), so ask about FTP or web access, and security issues with having so many people playing on one machine. Is this data going to be files or in databases? Is it ever going to be used to feed public websites, or is it private for internal business use (a data warehouse for small businesses)?