You don't have to violate anything in RFC6749, so technically yes. As I said it's not widely adopted, but it's also not difficult to implement. Generally OAuth2 client libraries require you to enter the client_id which you get during registration. Instead just tell them to use the URI of their app. You can see an example of such instructions for my LastLogin project here: https://lastlogin.io/developers/. It's just a short paragraph.