The Single License of Powered Keylogger implies the possibility to use the registration key on the two computers simultaneously. But only providing that the keylogger core driver is enabled only on one of the PCs.
So you can use your license key on the second computer with PK but make sure that when you install PK you tick only "Logs Viewer" installation and uncheck "Keylogger core driver" installation. In this case the two PK copies will work ok.