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

Linguists 101: Etymology is not definition. The fact that the word "proprietary" derives from a Latin word having to do with owners (and not as you've claimed from the English word property which comes via French) does not define the word.

A good rule of thumb is, if you think the meaning of a word is such that it is always redundant (as would be "proprietary" of software in this vague sense) then you probably have the meaning wrong. This follows from Grice's maxims.