They have stopped publishing the source code for their clients.

They have?

https://github.com/telegramdesktop/tdesktop seems fairly up to date?

Latest commit on the Android version was six months ago: https://github.com/DrKLO/Telegram

And yes, that's the official location of the Android app, linked here: https://telegram.org/apps

it seems they are watching, they've uploaded the newer version

Reproducible builds, and deploying my own server.

And a believable business model would be cool.