You should be able to find VIEW and DOWNLOAD links just below the EJS simulation to view/download the EJS source.
You should be able to open the ejs source if you downloaded the EJS jar file and also have installed EJS.
Double click the jar file to run it, [u]right click[/u] in the simulation region and select [b]open EJS model[/b], and the source will be opened in EJS.

You might want to check out http://physci.kennesaw.edu/mzoughi/Simulations.shtm for several similar simulations.