Although I'm not a member of the FHS and I post my own enquiries on the MGBB, I view this particular BB quite often and have posted a number of responses to enquiries.
It would be a real loss, particularly to members, if only members could post here. I agree with your comment about the main site and find it less user-friendly, but why restrict research on this basis?
I've no idea how much time you and others have put into your own excellent site and from a researcher's point of view can only thank and congratulate you on this but what about 100s of us who plod away with our own indivual family histories - we need all the help we can get and the more free available sites there are to share information the better.