Earlier quoted context omitted.
We've spend a lot of time optimizing the developer experience in postmarketOS by making easier tooling and writing more documentation, I'm glad it helps. While Debian has more strict policies on software licensing etc the musl component of postmarketOS pretty much makes sure that no closed source software will ever run in userspace. The main difference is that postmarketOS does deal with firmware for hardware while D…
Why prevent closed source software from running in userspace? Even in Fedora Linux I find myself having to use closed source software a lot for daily tasks.
Some distros, such as alpine Linux, use musl libc as their system wide C library.
glibc is pretty much ubiquitous, so any closed source software will be compiled against glibc and will not work with musl c libraries.
That's not to say a vendor couldn't do a muslc build of a closed source software, just that it's pretty much unheard of.
I believe binary compatibility is a goal of musl, being able to run a glibc binary against a musl libc library, but I think that's a long way off.
So an alternative on a musl libc distro is to use something like flatpak that bundles glibc libraries in a sandbox / container.
The side effect the grandparent comment is referring to, is that you have a good idea all the software on your system is open source, other than what you are running in flatpak, as closed source binaries are unlikely to run on your musl system.