You can use any system by integrating it into the plug-in system. The core-core structure allows a custom link structure for each plugin.
The wiki plugin that was made earlier contains the example you're saying.
this is possible, but you must edit oxwal and phpbb registration functions, where you add:
- on oxwall registration you must write code, which will be creating account on phpbb
- on phpbb registration you must write code which will be creating account on oxwall
When i retired from full time development i made my most popular modules free and put them up on the WHMCS forum for all to use.
If your a developer you can just download the module and youll see how it connects to phpBB (there is a file for each phpBB version) and creates the account.
I had considered this awhile back but i could not see why anyone would have a situation of needed to sign up for another forum when they have the one in oxwall, even if it is limited in features.
If there is a call for this i can do the plugin easily, but i wont do it for just one person. So you are welcome to download the free module for WHMCS and do what you can on your own or wait until there is more need and myself or someone else will do a plugin.