ET Book, the font used on the page, is free and open-source:

https://edwardtufte.github.io/et-book/

Modern browsers also have preferences to switch off web fonts.

The main downside of custom web fonts isn’t the licensing but having to download those fonts to render the page. There are ways to optimize font loading [1] but it can still lead to delay in rendering or font swaps.

It looks like ET-Tufte has already considered and tried to mitigate this downside. [2]

[1]: https://web.dev/optimize-webfont-loading/

[2]: https://et-jekyll.netlify.app/et-jekyll-theme/#performance

Licensing is a issue[0] in commercial fonts, though.

[0]https://twitter.com/typographica/status/1395769805542547461?...

> Just let me use my browsers' default!

Just disable fonts in the browser settings then.

I think it’s beautiful. It’s all subjective and they strived to add beautiful typography to this theme.

It is only natural to include a font which was commissioned by original author.