EISL was written by Kenichi Sasagawa
https://qiita.com/sym_num/items/793adfe118514668e5b0
The license appears to be similar to BSD/MIT to my non-laywer eyes: https://github.com/sasagawa888/eisl/blob/master/license.txt
It provides an interface to WiringPi, allowing control of the GPIO pins on a Raspberry π.

Free42 is a re-implementation of the HP-42S Scientific Programmable Calculator and HP-82240 Printer.
It is a complete rewrite, not using any HP code. It does not require an HP-42S ROM image.
Free42 is an Open Source project. The executables and source code are released under the terms of the GNU General Public License, version 2.

"ma" is a minimalistic clone of the acme[1] editor used in Plan 9, and is written in Tcl/Tk. It has been tested with Tcl/Tk 8.5, mostly
under Linux. "ma" has successfully been run on Mac OS X with XQuartz, but needs a tiling window manager to be used in a satisfactory way.

GNU Mes brings a Reduced Binary Seed bootstrap to GuixSD and potentially to any other interested GNU/Linux distribution, and aims to help create a full source bootstrap as part of the bootstrappable builds effort.

It consists of a mutual self-hosting Scheme interpreter written in ~5,000 LOC of simple C and a Nyacc-based C compiler written in Scheme. This mes.c is being simplified to be transpiled by M2-Planet.
https://github.com/oriansj/M2-Planet

The Scheme interpreter (mes.c) has a Garbage Collector, a library of loadable Scheme modules– notably Dominique Boucher's LALR, Pre-R6RS portable syntax-case with R7RS ellipsis, Matt Wette's Nyacc –and test suite just barely enough to support a simple REPL and simple C-compiler: MesCC.
https://github.com/oriansj/mescc-tools

Mes+MesCC can compile an only lightly patched TinyCC that is self-hosting. Using this tcc and the Mes C library we now have a Reduced Binary Seed bootstrap for the gnutools triplet: glibc-2.2.5, binutils-2.20.1, gcc-2.95.3. This is enough to bootstrap GuixSD for i686-linux and x8664-linux.

Mes is inspired by The Maxwell Equations of Software: LISP-1.5 – John McCarthy page 13, GNU Guix's source/binary packaging transparency and Jeremiah Orians's stage0 ~500 byte self-hosting hex assembler.

GNU Mes is free software, it is distributed under the terms of the GNU General Public Licence version 3 or later. See the file COPYING.

Interesting information about using the GPU of the Raspberry π.
In the forum thread https://stardot.org.uk/forums/viewtopic.php?p=152451#p152451 emulators for 6502 and other processors are discussed, even pdp-11 was mentioned.
More details can be found at https://github.com/hoglet67/PiTubeDirect/wiki
The pdp-11 emulator is in the 'egg-eater-dev' branch.

Overview of current (2018-10) compression algorithms.

Found via the review
http://www.radioforeveryone.com/2018/09/nooelec-ham-it-up-plus-upconverter.html

Flatpak is a next-generation technology for building and distributing desktop applications on Linux.

Found via computable-reals https://github.com/tarballs-are-good/computable-reals, but others such as Quickproject https://github.com/tarballs-are-good/quickproject are interesting as well.