Look on there homepage!
"GAIN Capital Group, Inc. acts as the counterparty for each forex transaction and as a liquidity provider to clients using its access to the inter-bank market. In doing so, GAIN Capital Group, Inc. assumes the risk associated with each transaction. A portion of GAIN Capital Group, Inc. and TradeStation Securitiesâ profitability may be the difference between the bid and the offer provided to the client, as well as GAIN Capital Group, Inc.âs ability to offset any risk transferred to GAIN Capital Group, Inc. by clients."