netBrush is a simple network based paint program.
This means it allows multiple people to draw on the same canvas at the same time. The feature set of netBrush includes a variable sized canvas and paintbrush and airbrush tools, changing brush size, hardness, color, opacity, etc. is also possible. You can also record and play back events send to the server as well as manipulate them, for example to scale up an image.
netBrush is based on SDL and doesn't use any external widget libraries, so it should be reasonably portable. In addition to the base SDL library netBrush also uses scons, SDL_net and SDL_image.