This is my post from this thread a little while ago. I am a lawyer. But this isnt legal advice, deffo get your own advice.
I'm posting my thoughts as a reply to yours just so no one thinks I'm picking on lawyers behind their backs.
Having been a serial entrepreneur in a previous life, always on the small business side of things, I thought I'd offer a perspective to folks regarding copyrights, trademarks, contracts, etc. that's not about right / wrong or legal / illegal, but rather a matter of practicality.
With no disrespect intended to my guitar slinging legal beagle friends, what people need to realize is one very important fact - the moment lawyers get involved, everyone loses. Except the lawyers, who get paid either way. I realize that sounds cynical, and lawyers deserve to get paid just like everyone else, but in the immortal words of Miyagi-san from Karate Kid, "The best way to block a kick is no be there." The moment you become engaged in a legal conflict, whether you were in the right or not, you're going to come out bloody to some degree.
People often think they'll prevail based on justice. In reality, a legal contract or any other such thing has very, very little to do with the outcome of a court case. It's typically down to, "my lawyer can beat up your lawyer" or even more often, "I can afford to pay my lawyer longer than you can afford to pay yours." The latter, in fact, is among the primary weapons of larger corporations with deep pockets, and often lets them get their way whether they were actually in the right or not.
All of which is to say that a well educated and comprehensive reading of the given legal statutes involved may indicate that you should be able to use a brand, trademark, copyrighted material or whatever. And yet, that doesn't keep someone from suing you just the same. And it certainly doesn't shield you from the legal fees you then incur from defending yourself.
So, the smart money is on the people who, as Miyagi-san suggests, avoid the conflict in the first place by not using anyone's brand names. Maybe there are cases where they should, legally, be able to do so. However, people rarely get sued for respecting other people's property.
I find it terribly clumsy to try and figure out which amp is what from these profiles. But I prefer that to seeing well intentioned people having to spend money defending themselves against legal action, spurious or otherwise.