You can install Poser 11 on up to 3 machines/OS instances. I had it installed on my desktop at work on my home desktop and laptop. Just can not run it more then one at a time. Most people won't run into an issue but beware that if you have a MAC and run a version of windows on it and install Poser to both OS' then that counts as two even if it is only one machine.

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