It *is* challenge/response, even though it's PACE.
It doesn't install anything extra on your machine, it's just a bunch of stuff written to registry.
So it is really safe to try the product. Of course, no installer means those things will be in your registry once you get rid of it (or purchase it... and it sure is worth purchasing). But afair (better make disclaimers from now on
), those are application specific enough not to cause any issues. There is 99.99% propability nothing will be disturbed by the registry entries, apart from another PACE protected thing (I'd love to say 100% but registry + flawed copyprotections... we've heard about those 
).So far, apparently nobody has suffered from the copyprotection? Apart from perhaps some bruised egos on message boards
Of course, there are other similar protections to this, I could contact them with suggestions about this. But the sad fact is that nothing remains uncrackable. The one I'd gladly suggest otherwise (really unintrusive, hard enough for most wannabe crackers to break) seems to suffer from an issue where it's possible to write a general patcher which just resets the demo period timer every time you want...
I've been doing some digging about different copyprotection systems for one project I'm involved in (not an audio product), and all I can really say that it's simply a waste of time if you're trying to affect the "warez" thing in any form. No matter what the manufacturers claim about their protection systems, there is no such thing as a working software-based copyprotection. Anything and everything can and will be cracked. The only somewhat functional systems aren't even a possibility for most software makers and will just cause more grievance and dependencies on uncertain factors and other annoyances relate to using the software (systems based on online authentication, dongle-based systems)...
But let's not get into *that* discussion, please. (Yes, "warez" and associated crap...)
In this light, simple serial would be preferable to c/r. As stated by some software manufacturers, copyprotections mostly stop the casual copying, "borrowing to friends" and so on. It hasn't nor it will stop the rampant piracy. Customers using software that have simple authentication schemes such a serial have been the most satisfied ones when it comes to copyprotections (excluding software that has no similar stuff at all).
It really is an amazing reverb. And I can't stop dreaming about seeing the other algorithms released in VST form in the future.
Regards,
JMH
It seems that the e-mail was first automatically forwarded to some specific person, but he wasn't awailable or something... Dunno 
.
).