XenForo 1.2 development is also under way. XenForo 1.2 will continue to add heavily requested features, improve the system for add-on developers, and workaround more complex bugs.
Not just that, but it's also written on the Zend framework (which vBulletin is not) with a very object-oriented approach (which vBulletin is also not). vBulletin was great for a while, but its codebase has become really stale, and in desperate need of a recode. Were I a XenForo dev, I think I'd actually be insulted that they were even compared. Besides all that though, vBulletin's parent company (whomever it became after Internet Brands) made the claim and filed the suit a day before any code was released to the public. They didn't even know what was in XenForo; I think this is all just corporate bullying. With any luck, the case will be thrown out.The copyright claims are in my personal opinion ridiculous.
Both the source code for XenForo and vBulletin version 3 and version 4 are visible source.
Everybody can look at it and realize that XenForo is written from scratch.