A CAPTCHA is a program that can tell whether its user is a human or a computer. The used reCAPTCHA is a free CAPTCHA service that helps to digitize books, newspapers and old time radio shows. This feature should improve the security for web based registrations. The patch uses the http://code.google.com/p/recaptcha/downloads/list?q=label:java-Latest libary which is under the Apache 2 license.
In http://www.igniterealtime.org/community/message/192657#192657 this feature is requested.
The svn diff command for my patch didn't work with the src/plugins/registration/src/web/registration-props-form.jsp file because it was marked as binary in subversion. So the attached diff should add the new setting page.
Guenther, since you've created this issue, you gained commit access yourself. Could you help me out releasing 3.6.5 and execute this one yourself?
Committed to revision 11482.