I am not sure. I only use IB and don't use external data provider, so not sure about price/availability. But I am sure if you Google around you might find a free source.
Yeah its free to open an account, but then you'll need to subscribe to data for each market.
I get the North American Futures/Options bundle (which includes NYMEX) for free because I generate more than $30 commission per month. Otherwise it would be $10 per month.
span, i have IB. it's minimum $10k to open an account, the data is free if you trade $30 in commissions. and you can withdraw your money after depositing it. account minimum balance is like $500 or something.