CubicSDR is a software defined radio system for Mac, Linux, and Windows. It’s at version 0.1.4-beta as of August 28, 2015, and you can download the binaries from https://github.com/cjcliffe/CubicSDR/releases/tag/0.1.4 or the source code from Github at https://github.com/cjcliffe/CubicSDR .
My point of comparison for software defined radio is GQRX. When you put CubicSDR on the screen it has a very pretty waterfall display and relatively easy to sort out mouse commands, but it’s lacking some of the fancier controls that a more mature program like GQRX has accumulated over time.
The interesting direction that CubicSDR is heading in is the product roadmap that is on its home page - in particular, importing and using digital modes that the liquid-dsp package supports, and additional visualization tools that would make a pretty display even prettier. The roadmap easily has a couple of years of development work, so there’s lots to look forward to.
CubicSDR supports the RTL-SDR dongles like my NooElec NESDR Mini 2, and it’s free-as-in-GPL, so it’s very much worthwhile to give it a download and see what it looks like.