Fluid dynamics, structural mechanics, electromagnetics, and acoustics. Automated Solution of PDEs
These cannot match COMSOL's ease of use or breadth of built-in physics interfaces, but they are completely free, legal, and actively maintained. Comsol Multiphysics 3.5a Free Download
In many online forums and websites, users have shared links to software packages and installation instructions. A search for "COMSOL 3.5a" can yield results like: but they are completely free