Which leads me to believe they are installing or running the Unity Runtime on their servers? If not I'd love a better explanation :)
If I write a licensed Unity app and run it on SpatialOS, well, that's now no longer allowed.
Unity had a pretty clear model as providing a software stack that one pays for using, primarily containing a bunch of proprietary tools for creating applications for their runtime. And then one could package that runtime and their application and give it to whoever one wanted (as long as they followed the revenue share part of the contract).
So yes it's part of the stack. but it's the part of the stack that people are meant to redistribute with their game.
It's like atlas vs ark, not like unreal vs unity
From Ars https://arstechnica.com/gaming/2019/01/unity-engine-tos-chan...
> The newly updated clause 2.4 of the Terms of Service now specifically excludes "managed service[s] running on cloud infrastructure" which "install or execute the Unity Runtime on the cloud or a remote server."
SpatialOS was basically re-distributing Unity under a SaaS model. Unity is in the right here.
Edit: Have heard some pretty good points about the ambiguous wording of the ToS (such as theoretically making the distribution of a Unity-made game through a storefront illegal). It will be interesting to see if this ToS change sticks.