The major problem was the retroactive aspect and the very short amount of notice. Part of choosing your engine is selecting the appropriate licensing costs for

The major problem was the retroactive aspect and the very short amount of notice. Part of choosing your engine is selecting the appropriate licensing costs for your games business model. After spending 2+ years working on your product, the business model completely changes, without the ability to opt out. It also affected already released games, and wasn't even a rev share, it would cost money just for downloads. This also occured 4 years after Unity publically stated that developers should be able to stay on the version of terms of service they already agreed to. If a company wants to have that business model, go for it - but don't bait and switch, don't go against your word, or else you've torched all trust between you and your customers