it's also a different type of legal moniker they seem to conveniently operate under
does a "marketplace" have the rules of a publisher or a platform? this is a fairly critical legal question lawyers would probably advise to not fuck up
publisher rules or platform rules then? which is it? it's a super-simple question to answer
marketplace is a place to sell stuff, that is the most common thing everyone agrees. So rules of selling and ecommerce apply. Since platform websites are mostly a website hosted by a domain with a provider this legal matter falls to the website owner and only agreements in the Term of service and/or Term of use with Privacy statement. Otherwise the domain provider is in legal trouble.
Now the tricky part, every country has different words for the ecommerce market. Even if you think you are safe there is a chance you might not be safe. I wont go over each county laws or rules for the ecommerce but they all agree that anything that sells online is called ecommerce otherwise it is just a normal website.
"e-commerce: business carried out by electronic means
A person providing an information society service is obliged to make available to the recipient of that service certain information. A service provider is under a duty to ensure that any commercial communications constituting or forming part of an information society service which he provides complies with certain requirements. A service provider is under a duty to ensure that any unsolicited commercial communication sent by him is clearly and unambiguously identifiable as such as soon as it is received and to provide certain information where contracts are concluded by electronic means unless parties who are not consumers have agreed otherwise. More practical substance appears in relation to DISTANCE SELLING. Special provisions have been made to facilitate certain aspects of e-commerce, see e.g. CONDUIT, CACHING, HOSTING.
Collins Dictionary of Law W.J. Stewart, 2006"
The rules fall under the law then the domain provider and lastly website owner. This is the simplist ways i could explain.
