Right, They don't. Amiga, Inc. ended the court battle with a settlement worked out and agreed to by Hyperion. Amiga, Inc. recognizes Hyperion as the sole owners of AmigaOS 4
Oh it's even more messy than that. Hyperion have the right to the binaries of OS4, but the code itself remains the property of the developers who wrote it (this is what happens when you don't pay your developers). This was tested and found to be true when the Frieden brothers successfully sued
Hyperion over the ExecSG code.
Licensing the trademark "Amiga" to a third party could be legally seen as diluting the settlement agreement with Hyperion. Not to mention damage to Hyperion's market by causing confusion in the marketplace due to the extreme similarity in the trademarks.
Hyperion could try, but tbh given the boneheaded moves they've pulled over the past 10 years, it'd be hard to prove damage to the market that wasn't down to Hyperion themselves.
Consider how well they've not done - in less than a month a guy selling re-branded Chinese zpc's has managed to garner more media attention than Hyperion has in the whole time they've been "developing" OS4.
Who should be sued? Why, Amiga, Inc.
Easy target given that they are at the present pretty much bankrupt.