this is OpenSim, a System Dynamics modeling framework released under the GPLv3. it is being (in)actively developed by Bobby Powers.

to run, install pygoocanvas and sugar. On Fedora 16 simply:

$ sudo yum install pygoocanvas sugar

and then a simple:

$ ./configure && make && sudo make install

should work, after which you can run the model editor:

$ opensim-gtk

and you should get a visual system dynamics model editor.

Frankly, I haven't worked on this in a while, but I wanted to get a mirror of the code from dev.laptop.org up.

The model editor allows you create diagrams and edit equations (by right clicking on elements). There appears to be some bugginess in there; after a while the diagram appeared to get 'stuck' for me. Also, moving around stocks after loading the goats example seems to be buggy. I haven't worked on this in about 2 years, so I'm not sure exactly what the issue is right now.

To run a model, save it in the editor, and then from the command line use opensim:

$ opensim examples/models/goats.osm

Eventually you should be able to run the model through the UI, but that isn't implemented yet.

for more information (although out of date), please visit http://www.opensimproject.org

Share and enjoy!