Change OS in VCard?

When looking at someone's vcard, there is section 'Operating System' (in polish 'System'). Is there an ability to set own OS text than getting from real OS ? I'd like to change my 'Fedora Core 3' name to ... other name.
I have source-version of tkabber. I don't understand Tcl/Tk very much, so could anyone tell me is there such a ability, and if yes, which line in a file to change to set own name?

Thanks in advance