While yes, that seems to be the case and would be smart for them to charge in the future to maintain the service. Unless the product is already mature, I'd say take advantage of a free offering while you can and until your are profitable enough to pay for a service. Can't imagine there are any 'real-time' offerings for market data. Companies like Bloomberg, Thomson Reuters, etc, etc wouldn't exist in the financial sectors if there was.

With regards to market quotes, latency is where companies like that compete. Good luck with your product or app.