Surely, the very branding of AROS as 'Amiga-like' means that its own developers consider it to be 'Substantially Similar' to The Software, that is, Amiga OS 3.1.
I know, but the developers will not decide whether it is "substantially similar", the court would.
Being -like something doesn't make you substantially similar. ReactOS has a goal of being NT-like... is it substantially similar? In execution or in code? What is the definition of substantially similar? IMHO, that term could be interpreted in any number of ways and make any court case very unlikely in this situation.