I think it's important to understand why such policies are in place.
I generally don't get involved with people who have DADT policies with their other partners. I always feel much more secure when there's open communication between partners and metamours. I can't help but tie withheld information with protecting insecurity. As a person who is usually the outsider dating people in established partnerships, I've found that DADT is usually the tip of an iceberg that usually causes larger problems for me when getting more deeply involved. If my partner's partner can't handle that kind of information about my involvement, then that usually means that, on some level, they can't handle my involvement period. So it ends up being the same drama, just buried underneath the surface where it simmers and builds rather than being evident and out there for everyone to address. For me, DADT ends up limiting how involved I can be with a partner.
The guy I'm currently getting involved with actually has a philosophy of "There's no such thing as too much information." And he means it. There's nothing I can't ask him about his other relationships, including all the details. The same for his partners- I can talk to them about anything without reservation. That's much more proactive and open than I've ever encountered before. It's also pretty lovely to experience.