I've followed these instructions:

• Unzip the compressed file into your Blender/Scripts/Addons folder.
• Start Blender.
• Open the User Preference Window and select Addons.
• Check the box to enable 'Poser Tools'.

However, I had to actually go to Install Addon... the Poser Tools 2 thingie didn't show up in the list until then even though I'd unzipped to the addons folder and closed and re-opened Blender. And it will not let me make it active (Enable Addon).

Blender 2.63 Final, Linux Ubuntu 12.04, 32-bit.

Monterey/Mint21.x/Win10 - Blender3.x - PP11.3(cm) - Musescore3.6.2

Wir sind gewohnt, daß die Menschen verhöhnen was sie nicht verstehen
[it is clear that humans have contempt for that which they do not understand] 

Metaphor of Chooks