My husband and I have been together for seven years. Only in the last year have we developed a level of comfort in which we've been able to discuss BDSM, and have been learning and discovering more and more about each others pleasures and interests. In that, we are both very fortunate to be able to fulfill each others needs and desires both physically and emotionally.
On another note, however, he also shares an O/L relationship with someone he met in chat several months ago. They have become very close friends and share everything from day to day activities to their most intimate "bedtime stories". He also has had several "flings" with others he has met in chat.
Is it cheating? IMO, it would only be cheating if he were trying to deceive me, and keep it secret. I feel that to cheat, there has to be a level of deceit or dishonesty on ones part. He has made all of his O/L activity aware to me, so I feel no level of threat to our relationship.