On the differences between Fedimint and Cashu from my perspective.

Fedimint is federated (meaning the ecash mechanics and the on-chain multisig), Cashu is always a single mint operator with Lightning abilities. Both are custodial in that sense. However, the rugpull risk is reduced in the federated model but it's also (often a lot) harder to implement as a programmer (it's a truly great achievement!).

Cashu is more about the ecash protocol itself. We're writing libraries in different programming languages and we have Python, Golang, JavaScript and Typescript so far. The goal is to design a simple ecash protocol that everyone can easily implement into their custodial Bitcoin application and benefit from the ecash protocol (near-perfect privacy and other benefits).

The first few examples so far are

* running a mint in LNbits