The only way you can violate the vB Licence Agreement if you post compleate or extensive blocks of vB Source Code. I know know about PostNuke, but as its free I think, I don't see any problem. Just make sure if you have used other peoples code/hacks that they get credit.
You can post it in the Beta Releases forum first so people can test it and then move it to the full releases when your sure its ready for "the masses" to install