OpenPGP.js

http://openpgpjs.org/

License: GNU LGPL v>=2.1.

E.g. used by https://www.mailvelope.com/ (License GNU Affero v==3) for Webmail

Completeness: ?

Compatibility: ?

Chromium Extension

• Google announced a Chromium extension that supports OpenPGP, see http://googleonlinesecurity.blogspot.de/2014/06/making-end-to-end-encryption-easier-to.html
• Heise newsarticle in DE: http://www.heise.de/newsticker/meldung/Google-experimentiert-mit-End-to-End-Verschluesselung-fuer-GMail-2215680.html