I have to be honest here, this situation is bothersome to me. From what I gather from foxflame's other posts, both her relationship with her husband and this new relationship with this married man are in a state of great change. Entering into new relationships while other people feel apprehensive doesn't seem to fit with the "consent of all involved" philosophy, or the "move at the pace of the slowest partner" philosophy. In short, this feels rushed to me, and seems doomed to failure. I feel for foxflame's husband and this man's wife. Not that I know them personally, but the way the relationship progressed so quickly is something that makes us new to poly relationships afraid of the lifestyle and the choices our SOs could UNILATERALLY make.
That is my 2 cents. Bash it if you like.