Ring (SFLphone) is an open-source SIP-compatible softphone and instant messenger for Linux, Microsoft Windows, OS X and Android. Developed by Savoir-faire Linux
License: Open Source
Zoiper is a versatile VoIP app that supports multiple protocols and offers a customizable experience, making it ideal for advanced users. Ring, on the other hand, focuses on ease of use and security with its cloud-based system, making it suitable for businesses looking for quick setup and integration.