1. Quite an unfriendly GitHub owner

They seem a little upset if you disclose migrating away from the software.

2. No disclosure of the source code, who knows what is in it and what it does?

You likely do not want to run this on internet-connected business machines holding and transferring customer data.

3. Try-hard jokes for actual users questions.

4. (Almost) everything it does, other FTPd’s can do better (the legal parts)

• Modern auth backends (LDAP, SQL, OAuth-ish flows)
• TLS, IPv6, security hardening
• General internet-facing FTP/SFTP use
• Maintainability and transparency (open source)

5. You open a closed-source service, which unknown developers from the scene part of the internet developed, to the internet and actually transfer and store confidential data on it.

Oof!

6. How does one get the idea to use that kind of software for business-critical applications anyway?

No idea. But it actually happened.

7. If that upset someone …

… please accept my apology in advance.