The BRL-CAD forums are hosted on Sourceforge. The forums presently available are:
Help This is the place to ask quick questions on using BRL-CAD. If you have an involved question, please consider using on of the support trackers instead.
Developer Discussion If you have a coding question, you should consider joining the brlcad-devel mailing list, but this forum exists for those individuals that prefer to have their questions answered more slowly.
Open Discussion This is an open forum for most any other topic related to BRL-CAD. The brlcad-users mailing list or support trackers are usually more effective.