Gould: Oracle to Red Hat: It's Not Your Father's Linux Market Anymore

To be honest, that meaning of 'proprietary' is a common one among 'business leaders', marketers, and similar bottom-feeders. They seem to use it to mean, vaguely, 'somehow better because we have magic brilliant people that nobody else has'. It's plain how this is related to the dictionary definition: it's also plain that it's pretty much entirely useless unless you're trying to market something to a group of people who think that 'proprietary' is in some way a good thing.