We have been using this captcha control with 2008.5 and it worked great. We recently changed to Telligent Community 5 and shortly after received a lot of spam registrations again :)Anyways I am no expert but managed to get the Captcha Control working the following way:\bin\Upupo.Captcha.dll\CaptchaImage.aspx\Utility\ContentFragments\Core\CreateUser.ascx (merge with the createuser.aspx file)
I am attaching my createuser.ascx file in case someone needs it or manages to clean it up / improve it further
0081.CreateUser.zip
Thanks akent! As I mentioned before CAPTCHA control do not have any dependencies on Community Server, so it should work for any version of CS.