> RustMailer is source-available. The code is open on GitHub, but requires a valid commercial license key for production use.

License Purchase: https://rustmailer.com/pricing

The mention of BSD/Apache is from here[1] and looks to be a listing of open-source licenses that this project uses.

[1] https://github.com/rustmailer/rustmailer/blob/main/license.h...

First, rustmailer is my GitHub username. Under this GitHub account there are two main projects: RustMailer and Bichon.

RustMailer is a middleware product with the same name. It is commercially licensed. I hope it can help developers save time on email-related development and also generate a bit of income for me, so this middleware requires a license key to run long-term.

Bichon, on the other hand, is an independent project built on the experience of developing RustMailer. It does reuse a lot of similar code, but it is licensed under the AGPL. These are two completely different projects. RustMailer provides many API interfaces similar to EmailEngine and is positioned as middleware, while Bichon is an email archiving (or unified search) project.

Bichon is positioned as a permanently free project. Users never need to worry that if you use Bichon today you will be asked to pay later — you can use it with confidence, and all of its code is fully open and transparent.

> Core Engine (Storage & Search): Tantivy[1] > Acts as both the primary storage for email content and the full-text search index. This unified approach ensures high performance and eliminates data redundancy.

[1] https://github.com/quickwit-oss/tantivy

Is what you're looking for a pretty good fit for how email was originally used? Or am missing something obvious

I’ve also been considering packaging it as a desktop application so that non-technical users can use it more easily, since there are Rust projects that can help wrap Bichon into a desktop app.