Doesn't that happen very often, that people work on such services?<p>I'm part of a small team that works on portier[0], which is what one could see as open source alternative to Auth0 (it's not the same thing, and it is more inspired by Mozilla Persona, but close enough). It's a service, as we run a broker online for everyone who wants using it, and the whole concept is having self-hostable brokers that handle the login of users (via email or Openid).<p>But: While that broker has a proper and simple API one can use to use the service with every language, it is still so much easier to just include a library/module that does that for you. Interpreting the jwt, fetching the jwk to check the signature, packing the request to the broker properly. We currently have one for Python, node, php and ruby/sinatra. They are not all at the same level, the one for sinatra does almost all the work for you, while the the python library is more a set of helpers.<p>And I don't think that's something weird we're doing, look at services like stripe or superfeedr, they all have language specific libraries to make calling their web part easier.<p>So what I'm saying: If you run a service that targets devs you might still end up writing language-specific libraries. And I don' think there is much keeping language-agnostic services from happening, as there are a lot of them.<p><i>Edit:</i> Though open source there is less, right. I think that's a mixture of the skills you need (having a proper server online and programming the software, not every team can both), the popularity of self-hosting in that community, and that it might cost money to run the online service.<p>[0]: <a href="https://portier.github.io/" rel="nofollow">https://portier.github.io/</a>