Their download page lists different payment tiers that include things like “Unlimited tracks” and “Z Series plugins”. I presume you get those features for a limited time with the trial.
On the other hand, I presume all those features are available to you perpetually if you build it yourself from source instead of installing from a prebuilt binary.
I just listened to it again, and it is definitely not as good as I remember it being. I was a fan of it, but I can definitely see how fans of either Korn or dupstep would have disliked it. “Get Up!” in particular is still just as good as I remember, though!