While many people use Skype for its free voice over IP (VoIP) services, Linux users have a love/hate relationship with it. Yes, Skype will run on some versions of Linux, but it doesn’t run on all of them, and the Linux version (2.2-beta) lags far behind the Windows version (Skype 5.3). That’s three major generations behind. Need I say more?
Much as I dislike Microsoft’s recent purchase of Skype and even though I think Skype’s technology is held together by bailing wire and duct tape, maybe Skype will become better for Linux with Microsoft. After all, it couldn’t be much worse!
That said, there are numerous Linux VoIP programs and they’re also free as in “free beer,” as well as free as in “free software.” Most of these programs use the open SIP (Session Initiation Protocol) standard or Extensible Messaging and Presence Protocol (XMPP) If they use the same protocol, you should be able to use one client to call another. To do this, of course, they must be on the same SIP or XMPP network. For example, I use the Ekiga.net VoIP network for SIP calls.