All online fx brokers provide a free charting program of some sort in order for clients to trade. Some brokers develop their own charting program isn't available at other brokers. Many brokers also offer/advertise 'pay-for-use' charting programs.
Brokers purchase
MetaTrader the developer MetaQuotes provide it 'free' for both
demo use 'live account' trading so no one doesn't need to purchase MetaTrader or pay a monthly fee to use the program.