Free ride dates back to 1880, while free loader is a more recent construction “freeloader (n.) also free-loader, by 1939, from free (adj.) + agent noun from load (v.)As a verb, freeload is attested by 1967 and probably is a back-formation from this”
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 ...
I don't think there's any difference in meaning, although "free of charges" is much less common than "free of charge". Regarding your second question about context: given that English normally likes to adopt the shortest phrasing possible, the longer form "free of charge" can be used as a means of drawing attention to the lack of demand for ...
Mashable on MSN: T-Mobile is giving away the Apple iPhone 17 for free — how to claim
T-Mobile is giving away the Apple iPhone 17 for free — how to claim
Lifehacker: T-Mobile Will Give You a Free iPhone 17e Right Now, No Trade-In Necessary
I traditionally have avoided tying my phone to a specific carrier, but I threw all my principles out the window when my local AT&T offered me a free iPhone 17 Pro if I switched, and traded in my ...
T-Mobile Will Give You a Free iPhone 17e Right Now, No Trade-In Necessary
MSN: Score a free Apple iPhone 17 right now with T-Mobile — how to qualify for this wild offer