Symphony.

Is this forum created with Symphony? If I wanted something similar to this with Symphony, is that possible?

I’d like to have a simple forum as a part of a website, with ability for members to log in but not see the backend. How might I do that?

Yes, this entire website is developed with and powered by Symphony. There actually is a fairly early build of one as an Symphony Ensemble that you can use right now. The catch is that this is an early build of the forum and it is not actively maintained.