I checked Garner's Modern American Usage; although BG doesn't address free of vs. free from, he writes that the distinction between freedom of and freedom from is that the former indicates the "possession of a right" (freedom of speech) and the latter "protection from a wrong" (freedom from oppression). So free from is used to indicate protection from something problematic, and free of (which ...
"Free of" vs. "Free from" - English Language & Usage Stack Exchange
grammaticality - Is the phrase "for free" correct? - English Language ...
Free entrance X chargeable entrance. Free parking X paid parking. Free service X chargeable service. Free consultation X paid consultation. Free health care X expensive health care. Free toilet X pay toilet. Free fare (in the sense of a free ticket to travel, the opposite can be a paid ticket). Here there is a mentioning of paying a ticket fare.