Mumble - Mumble is an open source, low-latency, high quality voice chat software primarily intended for use...
GOG.com - DRM-free game store, selling both new and old titles. No clients required.
Mohawk Voice - Mohawk Voice is a low resource, high quality VoIP program which is free to download and use.
itch.io - An online game marketplace and community.
Steam Chat - Steam Chat is a chatting app for Steam users that enables them to chat through their cell phones and get updated with what is happening.
GnuPlot - Gnuplot is a portable command-line driven interactive data and function plotting utility.