Currently there is no way to deactivate a copy of PM once it is activated. We're working on a new activation system that allows deactivations.
Do you have any ETA for this?
Will you issue new activation keys when the new activation system is ready?
Could you please answer my 2 remaining questions:
1) What happens if I decide to uninstall the PM from one machine and reinstall it onto another one?
2) What should I do if I lose access to the OS on the old machine (HDD failure etc.)
I recently had the same HDD failure problem with Adobe, but I managed to resolve it quickly by contacting the support. Can I do the same with the PM?