Interesting thread!
I didnt know about openbazaar.org, really interesting and inspiring for OFN.
I just learned that JSON-LD is actually compatible with RDF. It’s an implementation of RDF. That is great because we can forget about the abstract theory of semantic web and just use JSON-LD on our API 
I see two dimensions to it:
- JSON-LD to give meaning to the data - links to schemas, the @context tag for example
- HATEOAS - basically, links between related resources
Anyway, first, we need to clean up and define our basic REST API, then we can start to build these beautiful things on top.
Some interesting links:
- the first part of this article describes what a JSON-LD API looks like: https://sookocheff.com/post/api/on-choosing-a-hypermedia-format/
- or you can look at the standard itself: https://www.w3.org/TR/json-ld/#basic-concepts
- really interesting post about W3C/RDF vs JSON-LD history: http://manu.sporny.org/2014/json-ld-origins-2/