It's been 2 years. They have no specific plans to release the server code.[1] They won't say what's been done or has to be done.

[1] https://github.com/Pocket/extension-save-to-pocket/issues/75

On a software product note, "Pocket", the client-side product that does local-only interest analysis so it can get a full list of interesting articles from the server, and then locally filter out all the stuff you probably don't care about, is not "the server application that accepts volutary user submission analysis to determine what goes on the API response list with which categories".

No one ever talked about open sourcing the service that the pocket client relies on, as far as I can remember.

The main function of Pocket is saving pages to read later. Did Pocket even have client side recommendations when Mozilla acquired it?

Mozilla's claimed principles include privacy, interoperability, and free and open source software.[1]

[1] https://www.mozilla.org/en-US/about/manifesto/

1. Is it possible to use the open source Pocket client built into Firefox with any other server, e.g. by specifying another domain name in about:config?

2. Is there an open source implementation of compatible server software, that you could use to run your own server?

The answers to these questions will tell you whether Pocket is open source.