Proprietary means not open-standard/open-source.
I remember this coming up on tech news sites a few years ago when I discovered f.lux... this article also makes mention of the patent-pending nature of the software: http://readwrite.com/2013/09/23/flux-a-hack-for-your-devices...
And also, what in the world does "Proprietary, with free download. (with patent claim)" mean??