Alternatives to BuddyTalk Instant Messenger for all platforms with any license

Thunderbird

Thunderbird is a free, open source, cross-platform e-mail, news and instant messaging client. The project strategy is modeled after Mozilla Firefox.

Free Open Source Mac Windows Linux BSD PortableApps.com ... Haiku
Extensible by Plugins/Extensions Support for IMAP Built-in RSS reader Encryption ... SMTP integration Add-ons Calendar integration Extensions Multiple Account support Protected by Password Tabs Built-in Calendar Categories Customizable Delivery reports Extensible by Plugins/Extensions Free API Gmail integration Google Calendar integration Import from Google Reader Gui HTML Compose Integrated Chat Integrated Password Manager Integrated Web Browser Intuitive Legacy addons support Export to OPML Import feeds from OPML Organize mails POP3 Support Portable Secure File Sharing Support for POP3 Tabbed interface Support for Themes Add a feature

2004 Like
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 Windows Linux BSD PortableApps.com ... Xfce
Support for Multiple protocols Support for Multiple protocols Extensible by Plugins/Extensions IRC ... Plugins Supports XMPP Chat Messaging Multiple languages Multiple Account support Multiple chat protocols Portable Video calling Voice Call Xmpp Add a feature

1474 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 Windows Linux Web Android ... iPhone Blackberry iPad
Chat Facebook integration IRC Messaging ... Support for Multiple protocols POP3 Support Team Collaboration Twitter Xmpp Add a feature

277 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...
- 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/
Free Open Source Windows
Chat Support for Multiple protocols Twitter Add a feature

220 Like
Disa

Disa is your new messaging hub. Conversations from different services can seamlessly be joined together, or disbanded within seconds.

Free Open Source Android Android Tablet Kindle Fire
Extensible by Plugins/Extensions Messaging SMS Messaging Telegram ... Unified communications Unified messaging Whatsapp integration Add a feature

22 Like
aMSN

aMSN is a free open source MSN Messenger clone. aMSN attempts to emulate the look and feel of Windows Live Messenger, and supports many of its features.
- Discontinued
  The project is dead. The last release was on May 2012 according to SourceForge.
Free Open Source Windows Linux PortableApps.com
Group chat Integrated File Sharing Multiple languages Portable ... Tabbed interface Add a feature

24 Like
Beagle IM

BeagleIM is a lightweight and powerful XMPP client developed by Tigase, Inc. It provides an easy way to start using the XMPP Protocol (formerly known as Jabber) if...

Free Open Source Mac
Messaging Video calling Video chat Xmpp Add a feature

1 Like
4talk Messenger

4talk IM service is a complete IM service for communicating with your phone contacts using your PC in the office or at home. You can transfer files and messages and...

Freemium Mac Windows Web Android iPhone
No features added Add a feature

4 Like
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Gyach

Gyach is a GTK+ based Yahoo! Chat client.
- Discontinued
  The project seems to be no longer developed. Last version, v0.9.8, released in July 2004, can be still downloaded from the official website.
Free Open Source Linux BSD
Chat Add a feature

2 Like
Jabiru

Jabber client for Android.
- Discontinued
  The app has been discontinued. Last version, 2.2.2.1, released in May 2013, can be still downloaded from Google Play Store.
Free Android
Xmpp Add a feature

5 Like