I spent yesterday filling out more ideas on of what things I want to change in the Confluence wiki. I also did a more indepth review of how to write confluence add-ins, using their "Plugins". I included some initial thoughts on the pros and cons of different methods of extending their software.
The most interesting to me looks like the event listener that lets you write code that is notified when things happen. The only problem is that their architecture doesn't give the plugin code any way to veto the events, for example "Sorry, all your space is used up, you can't create a new page." So probably many of the things I want to do will require major surgery to their software..... I need to setup a java development environment to start experimenting with rebuilding the software, and get some dialog going with the developers on various things like: preferred way to add new fields to the database tables, how to deal with providing a custom compiled version of confluence. Providing source code hacks will limit my market only to those who have the energy to recompile the source, which doesn't include the majority of their users.
I also surveyed the various plugins currently available. None included anything related to billing, and I couldn't find any references to multiple different domains being rendered from a single installation, although I know I've seen that request, and saw one users comments on a partial solution involving apache url rewriting. Probably the reason for no other solutions in these areas I am interested in is that they will involve major heart surgery to the wiki core.