Open-source hard- and software for two-factor authentication.
I need to test them and want to understand the differences between versions 1 and 2. The articles
https://solokeys.com/blogs/news/trussed-announcement and
https://github.com/trussed-dev/trussed-totp-pc-tutorial look interesting.

Delta provides language syntax-highlighting, within-line insertion/deletion detection, and restructured diff output for git on the command line.
Found via https://tecosaur.github.io/emacs-config/config.html
There are other programs using the name delta, for example
https://guix.gnu.org/packages/delta-2006.08.03/
"Delta assists you in minimizing "interesting" files subject to a test of their interestingness."

Gqrx is an open source software defined radio receiver (SDR) powered by the GNU Radio and the Qt graphical toolkit.

Found via the Fossil forum https://fossil-scm.org/forum/forumpost/168b2bb05e

Wiki about the Slice media Player. Last updated 2015-11.

Solid (https://solid.mit.edu/)  was created by the inventor of the World Wide Web, Sir Tim Berners-Lee. Its mission is to reshape the web as we know it. Solid will foster a new breed of applications with capabilities above and beyond anything that exists today.

Solid (derived from "social linked data") is a proposed set of conventions and tools for building decentralized social applications based on Linked Data principles. Solid is modular and extensible and it relies as much as possible on existing W3C standards and protocols.

https://solid.inrupt.com/how-it-works
Within the Solid ecosystem, you decide where you store your data. Photos you take, comments you write, contacts in your address book, calendar events, how many miles you run each day from your fitness tracker… they’re all stored in your Solid POD. This Solid POD can be in your house or workplace, or with an online Solid POD provider of your choice. Since you own your data, you’re free to move it at any time, without interruption of service.

gphoto-sync is an open source command-line tool written in Python. It’s purpose is to backup Google Photos and Albums using the Google Photos Library API. Once setup, it can be run on a regular basis, to ensure all the pictures stored in the cloud are also stored locally on your own storage.

gpsctl is a utility program written for Raspberry Pi computers using a U-Blox GPS board. The author's rig is a Raspberry Pi 3 Model B with a Uputronix GPS board, which uses a U-Blox MAX-M8Q GPS module. Some of gpsctl's functions are generic for any GPS that streams NMEA data to a Linux serial port, and these should work on any Linux system. Most of gpsctl's functions, however, are quite specific to the U-Blox products, and use their proprietary UBX protocol (again, on a serial port).
Found on https://thepihut.com/products/raspberry-pi-gps-hat

TinyScheme is a lightweight Scheme interpreter that implements as large a subset of R5RS as was possible without getting very large and complicated. It is meant to be used as an embedded scripting interpreter for other programs. As such, it does not offer IDEs or extensive toolkits although it does sport a small top-level loop, included conditionally. A lot of functionality in TinyScheme is included conditionally, to allow developers freedom in balancing features and footprint.

WARNING: PROBABLY INSECURE
This is a version of drawterm (a program for connecting to Plan 9 systems) which runs in a webbrowser. To connect to the remote host, it uses Websockets, which means you need a proxy such as websockify.

Jsdrawterm is written in Javascript, but it uses a bunch of C libraries from Plan 9 (for crypto and drawing routines) which need to be compiled to Webassembly. Since the Javascript also deals with some of the crypto, it's probably horribly insecure and hackers will steal your cats.