Various players in the game.
End Users: non-developers, varying skill/interest levels
Member Sites: owners of, and developers for, destination websites. Some of these might like to charge for content or tangible products (books, cars, etc.).
Reference Sites: owners of, and developers for, sites which provide identification services.
Independent Developers: many are really employees/creators of Member Sites and Reference Sites, but I'm sure there's an "other" group that's relevant. Like those who like to build frameworks even if they don't have a big place to apply them. Like the Mono Project.
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