Getting the license is not only that you pay for being allowed to use the frequency. It's much more. It's that you know that you are unlikely to be interfered by a much stronger emitter in the neighbourhood and that you are unlikely to interfere others. It's the job of the license giver to manage the whole spectrum of electromagnetic waves so that no such overlapps will occur.

Be warned, if there's a military application at your place that would be interfered by your application, then this can become really uncomfortable for you. These military people don't make jokes...
So, be absolutely sure, that 433MHz is a suited frequency BEFORE you start.

There are certain tricks to detect the use of forbidden carrier frequencies, even if used intensities seem to be negligible. In many countries authorities are very effective in detecting the use of forbidden frequencies...

Kai