Well the signals are predictions made by professionals or not normal people in the trading field (people rating them will determinate that).
So when someone is well rated he can sell his signals for money (he will get buyers for because of his reputation), like saying "USD/BTC will go up 1.235545 at 4 AM".
It's more like a binary system where they predict "up or down" "0 or 1".
I'm not sure about this since I don't see something bad: someone "connected" to the domain selling his skills.
Still need to know if it's allowed in Islam or not.