I believe that someone is having you on.
The only way to "unlock" a PAP2 is to connect it to a network where you control the DNS service, and trick the adapter into downloading a hacked version of the configuration file, and then upgrading the firmware so it doesn't keep trying to "phone home" for the locked-in configuration when you place it on the live network.
No, I do NOT know how to do this, so please don't ask. If you want an unlocked PAP2, buy a Sipura 2000. It is functionally identical to the Linksys and isn't locked into Vonage, or whoever.