The Telegram client can just barely be considered Open Source, see the discussion at <a href="https:&#x2F;&#x2F;github.com&#x2F;DrKLO&#x2F;Telegram&#x2F;pull&#x2F;76" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;DrKLO&#x2F;Telegram&#x2F;pull&#x2F;76</a>