So the other member entities aren't party to any agreements signed by any one member, but they're definitely going to jump into any war begun by said member. That's quite the racket you're running. ;-)
No, not quite. There are restrictions on foreign diplomacy.
But, broadly speaking, it's a reasonable arrangement. We pledge to defend each others' borders. None of us are obligated to attack anybody on behalf of the others. And you'll notice D'Hara hasn't declared war: the terms of the Moot are really quite flexible as they regard foreign diplomacy. So, yes, as long as Terran didn't hit first, as long as we could plausibly be defending, D'Hara and Barca (and Asylon through a separate treaty) are obliged to support us.
None of those realms are obliged to support us in an invasion of Kabrinskia. And, so far, Asylon has pledged strictly defensive support, and I expect them to keep that commitment, D'Hara isn't entering the war at all, and Barca, even if they do help offensively (they have made no public commitments one way or another), is quite far away, so of only limited help.
