Jam is a graphical user interface for JoinMarket, and while obviously related, is a separate project developed by a separate set of people.
Jam is a free and open-source project that aims to improve the financial privacy of yourself and others, without relying on a trusted third party. It was started in 2021 by various volunteers and is still developed and maintained on a volunteer basis. As mentioned above, Jam is a front-end for JoinMarket, a privacy-focused bitcoin software that uses a peer-to-peer marketplace to facilitate collaborative transactions.
The goal of Jam is to provide an interface that makes JoinMarket easier to use, and thus more easily accessible for more people.
JoinMarket is a special kind of software that is aimed at improving the privacy and fungibility of bitcoin transactions. The main way to improve privacy and fungibility on-chain is via collaborative transactions.
A collaborative transaction requires the coordination of multiple parties. The right resources (UTXOs) have to be available in the right quantity at the right time.
Consequently, the problem that needs to be solved is not a technological problem, but an economic problem. JoinMarket solves this problem not by central coordination, but by creating a market that allows participants to allocate these resources in the best way, according to their individual needs.
About the Name
The name "Jam" is a backronym, stands for JoinMarket's Awesome, Man, and shouldn't be taken too seriously. However, it works on multiple levels (Let's jam the signal!) and "cooking jam" is also a fun metaphor for mixing something in a tasty way (and putting it in jars).
About the Philosophy
We believe that, in the long run, open protocols will survive. Platforms, on the other hand, are run by companies and all companies eventually go bankrupt.
The motivation behind Jam (and JoinMarket—and Bitcoin, for that matter) is to build something that doesn't go away.