Open Source Software for macOS
LibreOffice Calc
LibreOffice Calc is a free and open-source spreadsheet tool part of the LibreOffice software package. With LibreOffice Calc users can manage spreadshets with its native Open Document Format (.ods), CSV (.csv) and other common formats like the Microsoft Excel format. The software is openly developed by The Document Foundation and the open source community while being released under a combination of license including MPLv2.0 and a secondary license GPL, LGPLv3+ or Apache License 2.0.
FlexGet
FlexGet is a free and open-source multipurpose automation tool for all of your media with support for torrents, nzbs, podcasts, comics, TV, movies, RSS, HTML, CSV, and more.
Termius
Termius is the SSH client that works on both Desktop and Mobile. The application lets you organize hosts into groups while allowing share settings across users. Terminus uses end-to-end encryption to ensure your data remains safe and secure, while keeping connection and command history.
Thunderbird
A free an open-source email client developed openly by the Mozilla Foundation and the community. Thunderbird is easy to setup and customize and supports POP and IMAP. The email client comes with all features needed to search, filter, write and manage emails, but also have builtin support for live chat between contact and RSS/Atom feed reader.
Node.js
Node.js is a free and open-source JavaScript runtime environment built on the V8 engine. Node.js can execute JavaScript outside of a web browse and works cross-platform. The platform is used to power many JavaScript software project and web application in production today. Node.js is perfect for data-intensive real-time applications due to its event-driven and non-block I/O model.
Irssi
Irssi is a terminal based IRC client for UNIX-based operating systems. Irssi comes with IRC built-in and is multi-protocol friendly for module authors, it also support integration with SILC and ICB protocols via plugins. The application easily integrates with your window manager, your terminal emulator, your remote connection, your terminal multiplexer, your IRC bouncer and your IRC adapter. Allowing you to use Irssi virtually everywher throughout your system. Irssi is free software licensed under the GPLv2, available for macOS, Linux, BSD, Solaris, and Cygwin.
LispPad
LispPad is a simple, lightweight, IDE for developing and running Scheme code on macOS. The language supported by the integrated development environment LispPad is based on the R7RS (small) standard of the Scheme programming language. LispPad provides the a wide range of components inclduing a fully integrated Scheme interpreter, a large set of libraries, a text editor supporting syntax highlighting, smart indentation, parenthesis matching and text completion.
USBImager
A really simple open-source, GUI application that writes compressed disk images to USB drives and creates backups. USBImager is avalible for Linux, macOS, and Windows.