add license/language for thunderbird

README.md

@@ -454,7 +454,7 @@ Log management tools: collect, parse, visualize...
 - [ImapSync](http://imapsync.lamiral.info/) - Simple IMAP migration tool for copying mailboxes to other servers. ([Source Code](https://github.com/imapsync/imapsync)) `NLPL` `Perl`
 - [Mutt](http://www.mutt.org/) - Small but very powerful text-based mail client. ([Source Code](https://gitlab.com/muttmua/mutt)) `GPL-2.0` `C`
 - [Sylpheed](http://sylpheed.sraoss.jp/en/) - Still developed predecessor to Claws Mail, lightweight mail client. ([Source Code](https://github.com/sylpheed-mail/sylpheed)) `GPL-2.0` `C`
-- [Thunderbird](https://www.thunderbird.net/) - Free email application that's easy to set up and customize. ([Source Code](https://hg.mozilla.org/comm-central/file))
+- [Thunderbird](https://www.thunderbird.net/) - Free email application that's easy to set up and customize. ([Source Code](https://hg.mozilla.org/comm-central/file)) `MPL-2.0` `C/C++`
 
 
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