Mumble - Mumble is an open source, low-latency, high quality voice chat software primarily intended for use...
itch.io - An online game marketplace and community.
Discord - Step up your game with a modern voice & text chat app. Crystal clear voice, multiple server and channel support, mobile apps, and more.
GOG.com - DRM-free game store, selling both new and old titles. No clients required.
RaidCall - Free & Light. Setting up is fast and easy; with no need to rent or set up servers. Low CPU usage and minimum memory footprint allows for smooth, uninterrupted communication. im. Group Communication.
GnuPlot - Gnuplot is a portable command-line driven interactive data and function plotting utility.