I'll post this to general, because I think there may be several possible ways to go about doing this and perhaps some will come out of this discussion. I am wondering if anyone has thought of a way to charge users per post to their site, or --in my specific case-- found a way to charge users only if they start new threads?
One way to do it would be to charge users to become a class of user that exclusively has the phpbb permission to start new threads, but it would be difficult to automate this so that as soon as the user pays they have the capability. Instead, you would have to have users apply to a moderator, pay through the moderator, and have the moderator adjust their permissions accordingly. The other problem is that this isn't really a 'pay per post' arrangement, but more a 'subscribe to this account type' arrangement.
I need 'pay per post' because I want to set up a job find forum for my industry that allows potential employers to post paid threads for their jobs and job seekers to post replies free of charge. Employers could post ten job ads a day if they want to, but I want to charge for each of these and not simply charge a general fee for a privileged account.
Has anyone else found a way to do something similar? There do not seem to be any appropriate php bb modifications as far as I can see.