I agree with you about the term's original usage, but I don't think that is the modern meaning.

Usage varies, but most commonly "free market" refers to an economy that is not centrally planned. All economies have at least some level of central planning, as well as at least some degree of economic freedom for participants, so the term is somewhat like the usage of "right" and "left" in politics, where it just indicates which side of a center line someone or something falls. Any market on the free-er side of the "center" can be described as a "free market."

So it has basically just become an antonym of socialism. I don't think it necessarily implies anything about a tacit approval of rent seeking in the economy.