Are you sure it's the honor system? It seems to me more like a clever move to disseminate the software so that people are more likely to pay, particularly since he explicitly defines "continued use" as being whatever timeframe the user wants.

Adobe's Photoshop license doesn't do anything like this. If you crack it, you're breaking the rules.

I think it's a gray area, but it's undeniably true that paying for a license is a respectful thing to do at the very least.