Not really. The OS X kernel is based on the BSD kernel, but the BSDs do not have many of the requirements to run Cocoa apps. Most importantly, FreeBSD and the like do not have Aqua, OS X's graphical environment, so you would be unable to run apps that require it. However, many of the CLI apps have have been ported to and from Darwin, so you should be able to install many of the same command line apps that Mac users can.