There’s no risk to practice trading with the free trial. The traders who keep using TradingSim:
"TradingSim is a great platform for both new and experienced traders who want to improve their skills without risking capital. The ability to simulate trading even when the market is closed – at any time of the day or night – makes Tradingsim a unique and highly useful tool. We’ve found it especially helpful for those who are unable to practice during normal market hours."