Unity is a game engine that, for a long time, said "just pay us a monlthy fee to develop using our engine and we're square." then because EULAs and Terms of Service are slippery little bastards that are contracts but only benefit the owner they changed that to "Actually you're going to have to pay us a fee every time someone installs your game lol get rekt".

Lots of people are being about this, but, like, Marx did not fail to consider, and in Capitalism if you don't have a contract you have nothing. Signing a "contract" where one side can alter the terms to whatever they want seems... a bit naive but what you can you do?