By this point you've most likely downloaded and installed and have been using one of the editions of Oracle (probly Enterprise Edition). You've probly noticed at some point that nothing stops you from using functionality or asks for a key or warns you that your evaluation period is almost up. Thats because there are no enforcement mechinisms inside of Oracle! They expect you to be honest and don't bother you with with trivialities.
Even though Oracle doesn't enforce its licenesing on your system, they sure as hell have a lot of lawyers and plenty of time to enforce licensing in the real world. Don't pull a fast one on them unless you want to put your company at serious risk. I've never heard of a company being forcably audited but dont' risk becoming the first. Besides that, the honor system is much kooler than Veritas-like lock downs.