GNU/Linux distribution that is small and fully free/libre

Question

I need a GNU/Linux distribution that is:

• Small: Less than 500 MB (after installation) for the "base system" with coreutils and a window manager, ideally without having to uninstall a bunch of pre-installed software first.

• Fully free/libre: It must not automatically install proprietary software. That also means that it can’t use an unmodified Linux kernel (as it contains proprietary binary blobs), so it should use the Linux-libre kernel or something similar.

• Actively maintained: Security updates should be made available reasonably quickly for all supported packages.

Answer 1

Guix SD

(GNU's Not Unix)'s Advanced Distribution!

• Liberating. Guix is an advanced distribution of the GNU operating system developed by the GNU Project—which respects the freedom of computer users.
• Dependable. Guix supports transactional upgrades and roll-backs, unprivileged package management, and more. When used as a standalone distribution, Guix supports declarative system configuration for transparent and reproducible operating systems.
• Hackable. It provides Guile Scheme APIs, including high-level embedded domain-specific languages (EDSLs) to define packages and whole-system configurations.

Core download (USB/DVD installer) size is 245MB for 64 bit and 243MB for 32-bit

• It is fully free endorsed by Free Software Foundation. In fact a part of GNU Project
• It comes with Guix Package manager and uses GNU Shepherd init system.

Here are couple of screen-shots from official website:

Answer 2

Alpine Linux (Small, Simple, Secure)

Alpine Linux is an independent, non-commercial, general purpose Linux distribution designed for power users who appreciate security, simplicity and resource efficiency.

We use it to create minimalistic dockers, but it would work just as great when installed as a standalone OS.

It is mostly licensed under GPL2 and MIT:

As per distribution policy, we only ship software licensed under OSI-approved licenses that conform to the open source definition: https://opensource.org/osd in the main, community and testing repositories: software that is freely redistributable and modifiable, among others. This includes software that is written for Alpine Linux, which is generally licensed either under the GPL2 or MIT licenses. The nonfree repository contains software under other licenses, but this repository is not activated by default and requires a user to build the packages themselves: we do not distribute binary packages for this repository. All of the licenses for software we package and ship can be looked up on https://pkgs.alpinelinux.org.

Some licensing highlights for the Alpine base system (packages installed by the alpine-base metapackage, plus the kernel):

• Linux: GPL2 (https://www.gnu.org/licenses/old-licenses/gpl-2.0.en.html)
• musl: MIT (http://git.musl-libc.org/cgit/musl/tree/COPYRIGHT)
• busybox: GPL2 (https://git.busybox.net/busybox/tree/LICENSE)
• OpenRC: BSD 2-clause (https://github.com/OpenRC/openrc/blob/master/LICENSE)
• apk-tools: GPL2 (https://git.alpinelinux.org/cgit/apk-tools/tree/src/apk.c)
• alpine-baselayout: GPL2 (https://git.alpinelinux.org/cgit/alpine-baselayout/tree/src/mkmntdirs.c, https://git.alpinelinux.org/cgit/aports/tree/main/alpine-baselayout/APKBUILD#n9)

• alpine-conf: MIT (https://git.alpinelinux.org/cgit/alpine-conf/tree/uniso.c, https://git.alpinelinux.org/cgit/aports/tree/main/alpine-conf/APKBUILD#n9)

• busybox-initscripts: GPL2 (https://git.alpinelinux.org/cgit/aports/tree/main/busybox-initscripts/APKBUILD#n9)