Is Criptext really open source?

**Describe the bug**
I was trying to review the self-hosted version and only can find the mobile clients, not the backend.

on your website, https://criptext.com/en/about, (throughout many pages on the site) it states

_With Criptext we’re giving control back to the user. We don’t ask for trust, but rather promote people to verify, which is why we’ve made Criptext entirely open source.

**Additional information**
Is this another Protonmail/mailspring, where the front-end is opensource but not the backend? If so, that is a shame
Alternate ticket here, but doesn't seem like anyone manages the responses there so I will try on this repo.
https://github.com/Criptext/Criptext-Email-React-Client/issues/1511