If you are a Linux user and you want to make free or cheap calls through your computer, there are a number of VoIP applications that allow you to do that. There aren’t as many as a Windows user would find, but there are enough of good and well-built applications that come with your Linux installation to allow you to save money and have a nice communication experience through VoIP.
1. Skype for Linux
Skype is the most popular VoIP application, with nearly half a billion users. The reason why I put Skype on top of my list while it is not primarily a Linux open-source application is that it is backed by a VoIP service. This means that its use is straight-forward for free Internet calls. No need for SIP configurations.
2. Empathy
Empathy is the default communication application on many Linux distributions, including the very popular Ubuntu. It supports text, voice and video communication and is interestingly rich in features.
