There was a download of EM Zoo Simulation 6.0 on the developer's website when we last checked. We cannot confirm if there is a free download of this software available. We recommend checking the downloaded files with any free antivirus. The program belongs to Education Tools. This free program is an intellectual property of web.mit.edu. The following version: 6.0 is the most frequently downloaded one by the program users.
From the developer:
Simulates the interaction between charged particles, and illustrates the electric fields generated as a result. Charges in the Zoo interact via the Coulomb force, with a Pauli repulsive force at close distances and a damping force proportional to velocity.
You may want to check out more software, such as Switch Zoo, which might be similar to EM Zoo Simulation.