PyMol is definetly one of the most used molecular visualizers. For a long time PyMol has been distributed free of charge as a very old beta version and donators had easy access to newer versions (binary). However, everyone always had the possibility to get the sourcecode of PyMol and compile it himself to get a newer version free of charge. The accessibility of the source-code from the pymol website was always a bit occluded, yet visible. Since the passing of the creator of PyMol, Warren DeLano, the NY based Schrödinger took over this piece of software claiming to keep it open source. For now this remains true, but I sadly have to notice that access to the source code became even more opaque than before. Thus, here a simple link to directly download the source code from the SVN directory.

Next, untar and unzip the file and follow the INSTALL instructions in the INSTALL file.