GeoGebra CAS Calculator - Free online algebra calculator from GeoGebra: solve equations, expand and factor expressions, find derivatives and integrals
itch.io - An online game marketplace and community.
Dr. Geo - Dr. Geo, a software to design & manipulate interactive geometric sketches.
GOG.com - DRM-free game store, selling both new and old titles. No clients required.
Giac/Xcas - Free computer algebra system
GnuPlot - Gnuplot is a portable command-line driven interactive data and function plotting utility.