Not open source but chess.com app is brilliant, it's a freemium model - you can play for free - but they just keep trying to sell you tip and tutorials. Also s

Not open source but chess.com app is brilliant, it's a freemium model - you can play for free - but they just keep trying to sell you tip and tutorials. Also seems to have all the grand masters on there as players, Magnus ignored my request for a game though.