embedded Forum software???

I have a possible project that would be a Xojo Web app front end. It would join 2 user groups (user types) and then allow one group to ask questions of the other group after each side had logged in or created an account. Everything is pretty simple/straight forward until I started thinking about what kind of UI format and how the 2 connections would work - then things got a little stickier.

Until I did one of my frequent checks of the Xojo forum to see what was going on and realized they were really just talking about a user forum - quite a bit like this one for Xojo. Does anyone know of existing forum software that can be incorporated into a project after login and checking and as most would do but be more like a part of the overall site/project and not a separate site - like Xojo and the Xojo Forum sites.

I know this isn’t very clear but I had to sign a Non-disclosure agreement so I can’t (at this time - describe it in much detail. Basically just getting 2 controlled groups of folks together to talk. But with some fairly extensive controls.