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
Skype is a versatile app suitable for individual users and casual communication, offering a wide range of features for voice, video, and messaging. Ring, on the other hand, is tailored for team collaboration with a focus on project management and productivity, making it ideal for businesses and teams.