Go and read the source code on the GitHub repository that the page links to as "Downloads". There's a LICENSE.md there, and a fair amount besides.

As we are using hypertext, I thought it would be useful to throw a link in here... but following your instructions feels like navigating a paper map. I don't see LICENSE.md here: https://github.com/be5invis/Iosevka/releases

But alright, I realized you must download the archive to find LICENSE.md in there: https://github.com/be5invis/Iosevka/archive/refs/tags/v34.9....

The license is "SIL Open Font License, Version 1.1." from http://scripts.sil.org/OFL