Tuya platform asking for money! Is this real?

I have recieved two emails from tuya.com saying my subscription will end in a few days. Is this real? I thought development use was free of charge. If this is real, how do I extend the subscription. I ask because the tuya site is impossible to understand!

You can ignore it.
I got that similar mail last october, everything still works without paying

Excellent, many thanks.