Then so far, I count
Myself
mog262
Mertvaya Ruka
T2Paradis
Invictus
I guess if it takes a while to get enough for a WorldDip, we'll just do a Classic one in the meantime. As for the rules, this is what I understood:
1) War must be declared in public press one year before you can begin invading. So, you can't enter someone else's territory (not just SCs, but any colored provinces that don't belong to you) until one year after your declaration war.
1.5) You can enter someone else's territory without declaring war if you had previously made a military access agreement.
2) Alliances, DMZs, etc. must be announced in public press as soon as they are formed and instituted. I'm not too sure on what happens should one want to take a really nice stab at their ally. I was fortunate enough to have a wonderful ally in India the one and only time I played. I'm quite sure you just have to publicly break the alliance and declare war.
3) SCs can be claimed in public press. For example, England can claim Holland as rightfully English straightaway in 1901. Obviously, this can anger Germany and maybe even France. The act of claiming fosters war. That's the point. :)
I feel like I'm forgetting a lot so please, if anyone knows the rules concretely, don't hesitate to add or amend. But, bo, that game looks great from the messages. We had a guy who had made a graph with the flags of the powers and the relations between them, as well as named wars and victors. The game I was in did not have those random winter events though. Very awesome! Exactly what I was looking for.