James Holloway – 
There are many compelling reasons to use open source software, where the code behind an app is free for anyone to view or contribute to. There’s the obvious benefit that it’s free to use. It’s arguably more secure (thanks to the many eyes on the source code). It’s built solely for the benefit of users. And it may have ethical appeal over an app built by, say, a multinational corporation. This in mind, here are 10 of the best open source alternatives to the software we use on our computers every day.
1. Web browser: Firefox
Developed by the Mozilla Foundation, the Firefox web browser has been a mainstay of web users since its release in 2002.
Firefox puts privacy front and center. Its Private Browsing mode not only deletes passwords and cookies after a browsing session, it also detects and blocks tracking software now prevalent on the web.
It’s also highly customizable thanks to myriad extensions which can enhance bookmarking and password management, YouTube watching, online shopping and almost anything else you can think to do in a browser.
Its latest release, Firefox Quantum, purports to be twice as fast as before, with a memory footprint 30 percent lighter than Chrome. It’s also kinder to your laptop battery than Google’s heavyweight browser.
Firefox is available for Windows 7 or later, OS X and MacOS 10.9 or later, and Linux.
2. Email: Thunderbird
Also the work of the Mozilla Foundation, Thunderbird is to email clients as Firefox is to web browsers: a powerful open source alternative to the likes of Outlook and Apple Mail.
As well as email, Thunderbird can be used to read news and blogs thanks to its in-built RSS capabilities.
Like Firefox, Thunderbird can be heavily customized via its suite of add-ons which can add features like instant messaging, calendars or encryption, or simply enhance the look and feel of the app.
And again, just like Firefox, Thunderbird can be downloaded for Windows 7 or later, OS X and MacOS 10.9 or later, and Linux.
3. Instant messaging: Pidgin
Pidgin aims to be the free one-stop shop for all messaging needs, offering support for a number of messaging networks including AIM, Google Talk, ICQ, IRC, Bonjour and XMPP, with support for more via the use of plug-ins. (And forgive us if you’re spotting an open source theme, here.)
Sign in to more than one network and you see a unified contacts list so the networks in use are, to all intents and purposes, invisible.
Thanks to its global network of contributors, Pidgin has been translated into a vast number of languages, including Irish, Valencian-Catalan and Belarusian Latin.
The latest release has dropped support for MSN, Myspace and Yahoo chat. It’s supported on Windows and Linux.
4. Media player: VLC
The ultra-lean and fast VLC player from the VideoLAN Organization has been the go-to media player for open source users since 2001.
VLC plays a host of file types as well as supporting DVD, audio CD and VCD playback. MPEG-2, MPEG-4, H.264, MKV, WebM, WMV and MP3 are among the codecs supported, with more available thanks to (you guessed it) downloadable plug-ins, which can also be used to customize the appearance of the app.
VLC is available for Windows, MacOS and Linux. It’s also available for Android, iOS, Apple TV and a host of other operating systems.
5. Text editor: Notepad++
Sometimes a full-blown word processor is too much hassle or not fit for the job. Whether it’s jotting down some quick notes to writing reams of (presumably open source) code, a simple text editor may be all you need.
Built as an unofficial homage to Windows’ own barebones editor Notepad, Notepad++ adds a number of advanced features from tabbed documents, WYSIWYG editing and syntax highlighting (which is a must for software developers).
Alas, Notepad++ is only available for Windows.
6. Office suite: LibreOffice
But should you need a fully-fledged suite of office apps, the world of open source software has you covered in the shape of LibreOffice. It trumps the open source predecessor Open Office in its superior support for Microsoft Office file formats, including the ability to create and save more recent file types like DOCX and XLSX.
LibreOffice includes a word processor (called Writer, pictured here), spreadsheet software (Calc) and presentation software (Impress) as well as dedicated apps for diagrams and databases.
The software has come a long way over the years, so if you’ve tried open source office suites in the past and been put off by iffy formatting, modern day LibreOffice may be worth another look.
LibreOffice is available for the Windows, MacOS and Linux triumvirate.
7. Image editor: GIMP
GIMP, which stands for GNU Image Manipulation Program, is an open source alternative to Adobe Photoshop and a powerful tool for photographers, designers or artists needing powerful image creation or editing software. (GNU is a license which makes software freely available.)
It includes numerous powerful features pitched at photographers, including quick fixes for barreling and vignetting, retouching tools, black and white enhancements.
It’s an extremely powerful tool which offers a Python development platform to create editing automations. It’s available for Windows, MacOS and Linux.
8. Antivirus: ClamAV
Antivirus package ClamAV detects not only viruses, but also trojans and malware and keeps an eye on email, Office files, PDFs, software signatures and archive files such as Zip and RAR formats among others. It boasts access to a virus database which is updated several times each day.
A number of job-specific third-party tools have been built to work with ClamAV, including firewalls, proxy servers, file transfer tools and POP3 email servers.
ClamAV is available for Windows, Mac and Linux. It needs to be installed via a package or the source code, so it’s not as simple as downloading an installer, unfortunately.
9. Password storage: KeePass
Online security is a hotter topic than ever, and with the prevailing wisdom stating not to reuse passwords, keeping on top of all your logins is no easy feat. That’s were a password manager like LastPass, 1Password or the open source KeePass comes in.
It’s ultra-secure, using both the NSA-approved AES encryption standard and the Twofish algorithm co-designed by Bruce Schneier.
It’s not the prettiest, but KeePass is a lightweight yet powerful app worthy of consideration. It’s available for Windows, MacOS and Linux, and can be run from a portable USB stick.
10. Operating system: Ubuntu
It’s not for the faint of heart, but if you want to go fully open source, your best bet is to run an open source Linux distribution as an alternative to Windows or MacOS.
Perhaps the best-known and most user-friendly version of Linux is Ubuntu, which began life as an offshoot of the Linux distro Debian in 2004. It comes with the afore-mentioned Firefox, Thunderbird and LibreOffice pre-installed.
Unlike other Linux distros, software is easily installed by virtue of Ubuntu Software, essentially a built-in software store (with many of its wares available for free).
Though there’s never been an easier time to adopt Linux, caution is nevertheless advised. Replacing your currently-installed operating system straight off the bat isn’t advised. A dual-OS setup is a good way to test the waters.
(Source of this, and many other excellent articles: https://newatlas.com/best-open-source-apps/56366/)