First-party source: A source URL (Or perhaps even self-upload?) by a verified account of the artist.
Second-party source: Source URL suggests the commissioner/requester posted it (Or it's a requester/commissioner upload), or shared to the the recipient at the source/the person who uploaded it.
Third-party source: Unrelated entity hosting image, had zero involvement in the creative process behind the content itself.
I haven't found any topics discussing the potential application. However, I was recently discussing self-uploads from other boorus/mistaken application of third-party source, and thought that first-party_source would help to narrow down posts with unnatural sources like rule34.xxx, paheal, e621, gelbooru, sankaku, etc. wherever- Some artists genuinely upload to at least one of these platforms, and there's some who might post there exclusively. For tag gardening, it would be helpful to have first-party_source to filter out from searches of sources like these. That's the only application I'm going to bring up myself.
