Some of it could be cleaned up fairly easily - like the use of Yoda conditions and other anti-patterns, numerous spelling mistakes, dead (commented out) code, redundant casts, unused variables etc. But the major problem is no separation of concerns (business logic is tightly coupled with UI logic and Android framework dependencies), which makes writing any automated tests for the thing next to impossible right now. Resolving this issue would require major refactoring.
You probably missed the point here. Messenger is just a use case. The license is pretty liberal and you can reuse the code in pretty much any app, not necessarily Messanger. social, dating, customer support.
I don't think that post is accurate, perhaps because (based on the RSS feed) it is from 2015.
> Telegram’s source code is not an SDK or a library. [--] But to be fair, the messaging app doesn’t state they have an SDK. All they did is put their source code in the open.
