That is simply untrue. Amiga products are still being sold that have the Amiga check mark. Every copy of Amiga Forever that sells is being sold with the kickstart roms which show the Amiga Trademark on boot.
And? As I wrote, anyone can use it for anything at this point. The only reason why the checkmark is there on boot is because kickstart 3.1 (well, 2.0 really) had it there, and replacing it is not something as trivial as replacing some bitmap.
So, even if you ignore the fact that IP law is completely out of wack in such a way that you might get sued even if the trademark is abandoned, it wouldn't apply to the check mark since it is still in use.
That someone use it does not mean that it's a valid trademark. Noone has legally cared about the checkmark since the days of Amiga Technologies GMBH and Amiga OS 3.1 when it was featured on the reprinted manuals (original OS3.0 and 3.1 manuals had no checkmark on them, only the 5 colour stroke). The checkmark was abandoned in favour of the boingball once Amiga International came along, and along with the written escom "AMIGA" the boingball has been the only protected logo since.
I've had T-shirts made with Amiga checkmarks on (nice indigo coloured ones), various Amiga related sites use it - it's been public domain more or less since CBM was around to care. I have yet to hear about _anyone_ even getting note about use of Amiga checkmark. And from whom would such a note come from anyways? Cloanto? Amiga Inc? Haha - dream on. The boingball on the other hand, has been the subject of many threats throughout the years.
And anyhow - the Amiga checkmark exists in so many variants, that it doesn't really work well as a legal logo. The one I use on my excellent T-shirts have the coloured version of
this one on them, which is quite accurate compared to the one found on A1000. Opposed to the one used in bootscreens (which is limited due to hardware).
But by all means, if you think I'm wrong, feel free to sue me for infringement, or talk Cloanto or whoever into doing so.