Alternatives to Fire for all platforms with any license

Pidgin

Pidgin is an easy to use, multi-protocol chat client client used by millions. Connect to AIM, MSN, Yahoo, XMPP, and more chat networks all at once. It has built-in...

Free Open Source Mac OS X Windows Linux BSD PortableApps.com ... Xfce
Multiple protocols Multiple protocols support Extensible by Plugins/Extensions Supports XMPP ... Multiple languages Multiple Account support Multiple chat protocols Portable Video calling Voice Call Add a feature

1435 Like
Jitsi

Jitsi (previously SIP Communicator) is an audio/video and chat communicator with full end-to-end encryption that supports protocols such as SIP, XMPP/Jabber, ICQ/AIM...

Free Open Source Mac OS X Windows Linux Web Android ... BSD
End-to-end encryption Group chat iPhone/iPod sync Multiple protocols ... Multiple Account support OTR Video calling WebRTC Add a feature

273 Like
Franz

Franz is a free messaging app / former Emperor of Austria and combines chat & messaging services into one application. Franz currently supports Slack, WhatsApp...

Freemium $ $ $ Open Source Mac OS X Windows Linux
Multiple protocols Gitter integration Gmail integration iPhone/iPod sync ... Lightweight wrapper Multiple Account support Slack integration Unified messaging Add a feature

88 Like
Trillian

Trillian is an instant messaging app that works on phones, tablets, and desktops while keeping your chats neatly synchronized between all of them! We think conversation...

Freemium Mac OS X Windows Linux Web Android ... iPhone Blackberry iPad
Facebook integration Multiple protocols POP3 Support Team Collaboration Add a feature

269 Like
Adium

Adium is a free and open source instant messaging application for Mac OS X, written using Mac OS Xs Cocoa API, released under the GNU GPL and developed by the Adium...

Free Open Source Mac OS X
Customizable Multiple languages Multiple protocols OTR ... Tabbed interface Support for Themes Add a feature

329 Like
ICQ

ICQ is one of the oldest instant messengers. First developed by the Israeli company Mirabilis, sold to AOL, sold again and currenly owned by the Russian...

Free Mac OS X Windows Linux Web Windows Mobile ... Android iPhone Java Mobile S60 Blackberry Android Tablet Windows Phone iPad Kindle Fire
No features added Add a feature

64 Like
Empathy

Empathy is a messaging program which supports text, voice, video chat, and file transfers over many different protocols. You can tell it about your accounts on all those...

Free Open Source Linux BSD
Built-in File transfer Multiple protocols Video calling Add a feature

154 Like
- Discontinued Empathy is currently unmaintained. Last version, 3.25, released in August 2017, can be still downloaded from the official website.
Imo

Message and video chat with your friends and family for free. Features - Make high-quality video and voice calls on Android and iPhone - Send unlimited messages...

Free Windows Android iPhone Android Tablet iPad
Push to talk Video calling Voice Call Voice messages Add a feature

208 Like
Miranda IM

Miranda IM is the smaller, faster, easier instant messenger with support for multiple protocols. Designed from the ground-up to be resource efficient while still...

Free Open Source Windows PortableApps.com
Multiple protocols Portable Add a feature

224 Like
Miranda NG

Miranda New Generation is a successor of a popular multi-protocol instant messaging client for Windows - Miranda IM . Very light on system resources and extremely fast.

Free Open Source Windows PortableApps.com
Customizable Extensible by Plugins/Extensions Multiple languages Multiple protocols ... Multiple protocols support Portable Add a feature

43 Like
Gajim

The goal of Gajim is to provide a full featured and easy to use Jabber client. Gajim works nicely with GNOME, but does not require it to run. It is released under the...

Free Open Source Mac OS X Windows Linux BSD Xfce
Encrypted chat Group chat Multiple languages OTR ... Supports XMPP Tabbed interface Video calling Add a feature

51 Like
Digsby

Digsby is a multiprotocol IM client that lets you chat with all your friends on AIM, MSN, Yahoo, ICQ, Google Talk, and Jabber with one simple to manage buddy list. Its...

Free Open Source Windows
Multiple protocols Add a feature

219 Like
- Discontinued The application is not developed actively anymore. The source code has been made open for the community to take over but that didn't make any impact: https://github.com/ifwe/digsby | https://web.archive.org/web/20121205002331/http://blog.digsby.com/archives/1969/
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Psi

Psi is an instant messaging application for Windows, Linux, and Mac OS X that connects to the free, open XMPP network. Localized versions of Psi are available in...

Free Open Source Mac OS X Windows Linux BSD
No features added Add a feature

77 Like
iMessage

Love iMessage on your iPhone? You'll love it on your Mac, too. Messages lets you send unlimited messages to anyone on a Mac, iOS device, or Apple Watch. Your...

Free Mac iPhone iPad Apple Watch
Encrypted chat Group Messaging Add a feature

41 Like
YakYak

What does it do: * Send/receive chat messages * Create/change conversations (rename, add people) * Leave/delete conversation * Notifications * ...

Free Open Source Mac OS X Windows Linux Hangouts
Portable Add a feature

17 Like