Earlier quoted context omitted.
No. That article says you only need a DPO if you're a public authority or if you're processing certain data or you're processing very large amounts of data. I'm struggling to understand why that's unclear. Is it the use of "public authority or body"?
Monal is an XMPP chat system. User's messages are user data, and everything it does is processing that data, in the form of broadcasting it. I suppose as long as the data doesn't count as "very large", that'd be fine, but what does very large mean?
He's not handling sensitive personal data.
He doesn't need a DPO.
See also the derogation for micro companies:
https://gdpr-info.eu/recitals/no-13/
> To take account of the specific situation of micro, small and medium-sized enterprises, this Regulation includes a derogation for organisations with fewer than 250 employees with regard to record-keeping.