• http://schema.org/provider "The service provider, service operator, or service performer; the goods producer. Another party (a seller) may offer those services or goods on behalf of the provider. A provider may also serve as the seller."
• http://schema.org/seller "An entity which offers (sells / leases / lends / loans) the services / goods. A seller may also be a provider."
• seller is currently marked as a subproperty of participant (an Action-oriented property)
• http://schema.org/participant "Other co-agents that participated in the action indirectly. e.g. John wrote a book with Steve."

My motivation here is that I still cringe every time I see 'seller' in non-commercial Offer descriptions, notably library holdings data (#733). Using 'provider' would seem more natural. I'd suggest revising 'seller' description to note that non-commercial offers can be described via 'provider'.

See also #424 #620

/cc @RichardWallis @dbs @vholland @chaals @rvguha @pmika @mfhepp @shankarnat