The Smith Micro versions had a deregister option.  That has been removed from what I see.  IIRC you can install on up to 3 machines, and as long as a suitable period of time has passed and a machine has not sent I am here message back then you can install on another machine.  Just don't install in a small time frame such as one today another tomorrow and the third the day after that and you should be good. 

Poser 5, 6, 7, 8, Poser Pro 9 (2012), 10 (2014), 11, 12, 13