SubSim is a project mainly written in C, it's free.
SubSim:
Compile Command (GTK+): gcc -Wall .c .h -o main -lGL -lGLU pkg-config --cflags --libs gtk+-2.0 gtkglext-1.0
Uses main.c as main file
Backup to GitHub Command: git commit -m; git push https://[email protected]/mattsbox/SubSim.git master
Compression Command: rm SubSim.tar.bz2;tar -cjvf SubSim.tar.bz2 ./*