A forex broker has the responsibility of carrying out trade on behalf of his client trader. He does the job of executing the buy and sell orders for the trader concerned. Forex brokers normally operate in an OTC (over-the-counter) market so that very less rules and regulations are binding on them and they can work according to their will.
Now, how does the forex broker make money? These brokers charge their clients a basic commission for each trade or spread. Broker’s spread is basically the gap between the ask and the bid price of the transaction. There is no bondage on the broker to charge either a commission or a spread. He can, at anytime, charge both of them from the client.
There may be a possibility that some traders offer to work on commission-free basis for clients. But this is basically a way to fool the traders, as such forex brokers earn their revenue by widening the gap between their bid and ask prices.