Is Criptext really open source?

[cheerios911]

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.
Criptext/Criptext-Email-React-Client#1511