statgas is a simple program to simulate the diffusion of an ideal gas. It is written in C and used the cross platform graphics libraries SDL and SDL_gfx.
For a description of the command line options, see the README
The binaries and source code of statgas are distributed under the MIT license. It allows anybody to use, modify, and copy the software without owing anyone, as long as they distribute/maintain the copyright notice and license text. There is no warranty, so you can't sue if it blows up your computer.
You can find the exact text of the license here: LICENSE.