Comment by matheusmoreira

You're absolutely right, it is not portable to other operating systems. I have written about this portability and system call stability here on HN a few times, at some point I decided to compile all the information into a post on my website.

https://www.matheusmoreira.com/articles/linux-system-calls

I started lone (and previously a liblinux library) in order to make applications directly targeting the Linux system call binary interface. I chose Linux precisely because it's the only one with a stable interface.

I currently have no plans to make lone a portable programming language.