Re: reCAPTCHA for registration
This is how to install SI Captcha globally on WPMU.
Step 1: upload the /si-captcha-for-wordpress/ folder and all it’s contents to /mu-plugins/
Step 2: MOVE the si-captcha.php from the /si-captcha-for-wordpress/ folder to the /mu-plugins/ folder.
Please report back here is this worked for you.