These people could just install Truphone on their softphone or ATA to receive phone calls with their Truphone number. UK users of a Nokia N95 with crippled VoIP could avoid their problems by using Truphone together with the 3rd party software Fring. I guess Truphone was not too happy with that since one of their revenue streams is call forward: When you are outside a Wifi area Truphone forwards incoming calls on your cost to your cell phone number and takes its share from these costs. Unless you have a US mobile phone number, then the call forward is free.
If you have installed Truphone 3.0 it's now impossible to find your SIP password on your mobile phone. At least unless another hacker finds another way to retrieve it. I can't reveal how it had been done before, since there are still users of version 2.0 who could make use of it and therewith violate Truphone's terms and conditions:
You may only use the software and service with compatible handsets or devices identified on our website www.truphone.com. You must check the list of handsets on the Truphone website to ensure You download the correct software for your phone. Truphone is not liable if You do not have a compatible handset or if You have downloaded the wrong version of the software for your handset. Truphone reserve the right to terminate this agreement should you be using the Truphone service with a handset or device that is not identified on the website as compatible.
I suppose that call forward and interconnection fees are Truphone's way to fund their recently anncounced free mobile calls to 40 countries around the world for the rest of the year. That's why they are so happy to have won the court injunction against T-Mobile which had blocked calls to Truphone's new numbers. More insight on the issue and how Truphone earns from calls to it's numbers can be found here.