I have a few coins that I love and made some T-shirts with their logos and my down design incorporated with them. I showed some people and they are interested in buy. Are logos copyrighted or are they public domain? Can I open a shop with products having alt-coin logos on them? or would I need to contact each developer team?
You won't get a simple answer here. Read this:
https://www.wikihow.com/Find-Out-if-Something-Is-CopyrightedIf it is copyrighted, you need permission, or you can sued back over many years, raking back everything you ever made in profit.