Downloading ACL2s 4.4.2 for Mac from our website was free. The software relates to Education Tools. Our antivirus analysis shows that this Mac download is virus free. This free software for Mac OS X was originally produced by Georgia Tech Research Corporation and Northeastern University.
From the developer:
ACL2 is a powerful system for integrated modeling, simulation, and inductive reasoning. Under expert control, it has been used to verify some of the most complex theorems to have undergone mechanical verification. In addition to its maturity and stability, these qualifications make it a good platform for learning about industrial-strength theorem proving.
You may want to check out more software for Mac, such as ScienceMatrix, Enzyme X or CUDA, which might be similar to ACL2s.