I'm the founder of both the Prosody and Snikket projects. Sorry about triggering alarms :) I can try to explain...
Prosody is a popular choice of XMPP server software. It's used for all kinds of stuff, from self-hosted chat servers to powering Jitsi Meet, to Internet-of-Things applications.
Prosody is extremely flexible, and has a bunch of configuration options that allow you to adapt it and extend it however you want. For some people, this is ideal. Those people should continue using Prosody.
Snikket has a different scope. It is specifically an answer to a question like "How can I easily make a self-hosted WhatsApp/Signal for my family/friends using open-source software?"
- Snikket contains Prosody, for the core chat part. But it's Prosody with a very specific configuration, and the configuration is part of the project, it's not intended to be modified by the person deploying Snikket. They only need to provide the domain name.
- Snikket also includes additional components that a modern chat service needs. For example, it includes a STUN/TURN server to ensure that audio/video calls work reliably (again, preconfigured).
- Snikket provides its own apps, which are tested and developed in sync with each other and with the server. This avoids the common problem of incompatibilities that occur when you have an open ecosystem such as XMPP, where different open-source project developers may develop features at different paces, leaving users to figure out which ones support which feature. It also solves the discoverability and decision fatigue for users (searching "Snikket" on an app store will get you an app that you know is compatible with your Snikket server, you don't have to go through a list of XMPP clients and figure out which one is suitable).
- Snikket servers are not designed to be open public servers (these are an administrative nightmare). Instead, your server is closed and private by default. As the admin, you choose who signs up to your server by sending invitation links. The invitations also serve to simplify the account setup process - no need to prompt users to "choose a server", etc. They just need to provide a username.
Projects such as Conversations differ by running a single public server (conversations.im) and guiding people to sign up on that server, or choose one of a long list of free public XMPP providers. In some cases that's all what you want. But onboarding a group of people that way is not fun (for example, they all have to share their addresses with the group add each other to their contact lists one-by-one - Snikket makes discovery of contacts within the same server automatic).
Beyond these things, Snikket is all open-source and XMPP. But there is a focus on making a good polished and secure "product", if you like, rather than supporting the entire diverse XMPP ecosystem which includes a range of software of varying quality (weekend projects and more recently, 100% vibe-coded clients). For example, Snikket servers require certain security and authentication features which some older codebases that have fallen far behind modern XMPP standards (think Pidgin, etc.) simply don't support today.
> it’s actually all based on prosody and conversations?
As mentioned, I develop Prosody. I also collaborate with the Conversations developer and other XMPP projects. There's nothing shady here. The goal is just to make a best-in-class XMPP project that solves one particular use case (and it was primarily my own use case to begin with of course - I wanted to move my family off WhatsApp).