DADT is Don't Ask Don't Tell. Typically, spells trouble because someone is going to figure something out and feel badly. No honesty or transparency.
The rest is that London is saying they do NOT date mono people. Only non mono people and no one that can't possibly be a long term relationship.
Not that they have to be a primary or major relationship off the bat, but if there's no room for growth into a long term relationship they aren't interested.
Me: Late 30s pansexual poly.
DH: My husband of 19 yrs and father of 3 teen girls.
DC: LDR of +4 year