Just do it, and wait for a cease-and-desist.  Then you'll know who you have to pay a license fee to.  Better to ask forgiveness later than ask permission first, right?  

Actually, that's terrible advice, don't listen to me.  But good luck figuring out who the proper owners are in that legal nightmare, and actually getting a response from them!  

Depends on your country law , what international copyright treaties
your country (well EU maybe , maybe not) signed , what shape and
words you plan to use etc etc ...

Most likely you can unless someone else is already selling T-Shirts
because most of those call them companies are registered either in
computer hardware or software field but there are more than one
company that would send you legal warnings.

Best way to do it is to try and register a company (:roflmao::roflmao::roflmao:)
and if you manage to register say AmigaSmart company with amiga like
logo in your country (that is registered only for selling clothes) then you are probably good to go because registration office will have to do legal checks and even if they miss they must stand by their decision later.Purpose of law isn't really to stop commerce , right ?

I think you could open a stand in Norway and sell them no problem.
I know for a fact that even though China passed copyright law in 2013
you could still make them there :lol::lol::lol:

For Commodore related items you need a licence from Commodore Licensing BV: http://www.commodorecorp.com

For Amiga logo, then you will need to talk to Amiga,Inc.

Why are those facts that were never proven in court of any country
always quoted ?

When someone send a warning to sue and the other drops project that
doesn't prove one right or wrong.Both companies are in US , US is not
Norway nor does it rule it.The one who looses in court is the one who is
wrong and will pay all expenses for the other side (and the one who would
loose is the one who thought he had more legal rights than he had in 99 %
of cases).

Only good advice if we are being serious would be to hire a lawyer in your
country to do all legal checks and inform you of your rights but in that
case you need to pay for that (it's not court case , court case only occurs
when two parties have dispute).

Can anybody spell, "merchandising" for me?

Well it may depend as much as the price of your car.You may even
ask different price/conditions  for different people but I don't think
you will even get a chance to get one let alone that if you would
get Amiga Inc. license you still could get "love letters" from someone
else.

Short story on how IP trolling works : You take your money to bank and
bank pays you interest.Does your bank go and rob other banks to get
that money ? Maybe ... What banks , big groups of investors and such
things do is buy assets.IP is good asset to buy because it doesn't need
high cost to keep value and they usually buy when value is very low and
wait for value to rise to sell and make profit.

Making things with it is secondary , they do that to be able to register
IP again although it's not a must.Meanwhile they can also sue people
for money.

ANy know what the price is for a amiga licence. ?

Quoting Dr. Evil, "One MILLION Dollars".