You can find the releases here, and if there is a delay it is only a few days at most:
https://github.com/Telegram-FOSS-Team/Telegram-FOSS/releases
Only the clients are open source, but anyone could use the source code to create their own network.
https://github.com/Telegram-FOSS-Team/Telegram-FOSS/releases
Only the clients are open source, but anyone could use the source code to create their own network.