Thanks at Niels, who pointed me to Ekiga after my last Videocast. Today I installed it and after re-emerging pwlib with the v4l and v4l2 use-flags I was able to set up my camera with Ekiga. I applied for a new SIP account at ekiga.net, because it was the easiest thing quickly, but soon I’ll try to use my default SIP account with it.
I was able to talk to my family having Gentoo Linux and Ekiga 2.0.9 at my side, and Windows Vista with Ekiga 2.0.11 Beta at the other. Cool!