My guess is the audience of this readme are not the users of the programming language but people who want to work on the programming language.
The current landing page lists features [1], and if my memory serves me the original landing page 15-ish years ago did not primary focus on an install guide. I can't check right now, since Wayback Machine is still down.
What also could happen with repository readmes is, that the sections devoted for explaining the language moves to github pages or a landing pages hosted somewhere, and the sections with install guides stay in the readme, as they are useful for people who want to contribute to the github repo.
The current landing page lists features [1], and if my memory serves me the original landing page 15-ish years ago did not primary focus on an install guide. I can't check right now, since Wayback Machine is still down.
What also could happen with repository readmes is, that the sections devoted for explaining the language moves to github pages or a landing pages hosted somewhere, and the sections with install guides stay in the readme, as they are useful for people who want to contribute to the github repo.
[1] https://boo-language.github.io/