Future versions of the UBB will have some payment features built in, however I'm unsure of if or when Rick will have the time to contemplate a version to work on with this.
As for the limiting of bandwidth or downloads, thats a bit beyond the scope I think, theres no real way to monitor if a user finished a download and the file system built into the forums just logs how many times a file has been downloaded versus who did the deed...
I'd immagine any "full" user could share their username and password with their friends, but onlyt hat username woudl be able to post; it'd happen must about anywhere with member area access, and is quite common and there isn't any way of stopping it unles syou where to monitor the account for access from various ip's.
I'm hoping that we'll have some sort of basic built in gallery by 7.2 in which there may or may not be some sort of payment module built into the UBB; this would allow for various usergroups to be able to have more access to sections than the standard "users" group.
