So how are you able to provide this for free? What is the catch?

There is no catch. We have two additional fee-based services - Personal KeyCAPTCHA and Extended Account.

Personal KeyCAPTCHA:
You are welcome to use our standard set of KeyCAPTCHAs offered by our service for free. However, if you are willing to make your site really unique one, you should use our additional service Personal KeyCAPTCHA. This service allows you to create your own captcha which will have an ideal match with the look&feel of your site. If your site is on e.g. fishing you’ll be able to create a CAPTCHA where visitors of your site are offered to place fishermen in a boat. More information about Personal KeyCAPTCHA you can find at https://www.keycaptcha.com/whatisit/?s=pc

Extended Account includes the following services:

• "Filtering of Anonymous Proxies" is a unique service KeyCAPTCHA . It allows to block messages from visitors using anonymous proxy servers. The list of anonymous proxy servers is updated every hour and contains thousands of unique addresses spammers usually use to work. This service drastically enforces the anti-spam protection of your site even against manual (by human) spamming.

Best regards,
Maxim Vladykin
KeyCAPTCHA Support Team

Hello Dear Members of vBulletin,

Doesn't anyone like KeyCAPTCHA?

It really stops spam-bots. Could you please try it in your forums and rate our Add-on?
We are open for your suggestions. And we do our job just for you.

Thanks in advance,
KeyCAPTCHA Team

Opera 11 beta Build 1128 and Windows XP Pro SP3.

Hello Robert,
First of all thank you for your feedback.

1. Could you please specify the version of your Flash plugin too?
2. Do you have any additional plugins in your Opera? If so please specify them all.
3. You see KeyCAPTCHA in all other browsers, don't you?

We will test it with the same configuration tomorrow.

P.S. We have adjusted the colors in each CAPTCHA task.

Thanks in advance,
Maxim Vladykin
KeyCAPTCHA Support Team

really difficult... captua..
i guess we need to hire cosultant to understand the new user, that how to use this captua... never mind..

but on other side it is great work to prevent the spamers as well as users too....

Isn't one of the number 1 rules of web design that if you have to tell the user how to use your site, it's too complex? Whatever.

I, personally, really like vB's question functionality. I think I will have to pass too, though.

This is a lot more fun that normal CAPTCHAs

This is a great idea and has huge potential, but as it is, it's too complicated. I'm fairly certain that if you did a test of registration rates, some of the more complicated pairings (e.g., matching the horses to the carriages) would show a significant decrease in registrations.

It would also help a lot if the English were correct.

You might get more exposure on this if you release a VB4 version on vb.org and include stop spam in your title as many users will no doubt be looking for hacks on vb.org since reCaptcha has been cracked.