Hey guys, I'm the developer for the official reCAPTCHA WordPress Plugin and it works well in regular WordPress but I've been getting many requests to make it work on WPMU. Since I haven't been able to find much documentation (I also tried getting help on the wp-hackers mailing list) and because I don't really have a great understanding of WPMU, I'm having trouble doing this. I think I'm almost done making it compatible I just need someone to test it and tell me how it goes.
This plugin allows one to put a reCAPTCHA on the registration page, the comments form, and/or hide emails from spammers using MailHide. I think the main difference when adapting to MU is changing the place where the plugin options are (Because people want it to be in the mu-plugins directory so that it's force activated) so that they appear under the site admin section or something, I believe I've done that. Also the main change I must do to the plugin is change the hooks I hook onto for the registration page. I've already done this as well, and I'm now using signup_extra_fields and wpmu_validate_user_signup. The former to display the reCAPTCHA and the latter to see if it's correct.
The only last confusion I have is the mu-plugins directory. Am I allowed to put the entire wp-recaptcha folder in there? This folder includes the actual plugin wp-recaptcha.php as well as the PHP reCAPTCHA library recaptchalib.php, a stylesheet, and a few other things. Or am I supposed to put the plugin wp-recaptcha.php in mu-plugins and also a copy of the wp-recaptcha folder (Also including wp-recaptcha.php) in the wp-content/plugins folder? I would appreciate any clarification you could provide.
Like I said, I'm nearly done (Or so I believe) making this MU compatible after having looked at the MU code and other MU plugins. If anyone would be so kind as to test the latest revision found at http://svn.wp-plugins.org/wp-recaptcha/trunk/ I would greatly appreciate it.