A simple answer is to ask the broker if they would allow you to redistribute the data - alot of brokers give their feeds out to comparison site e.g. myfxbook, but i'm pretty sure they have consented to the data being made publicly available.
Also remember if you are just displaying FX data it should not be a problem as their is no central exchange, your only risk is that they just block access maybe if you are using it for commercial purposes, for example making money from your site.. if you are displaying CFD data such as the indices, commodities etc.. you should be careful as most of these CFD prices are derived from the exchanges like CME and ICE and you will have them coming after you to pay fees!
