Hi, that is right, only it isn't "CAPTCHA", it is a PHPBB anti-spam mod. I have had to help a few iPad people get registered. It should be fine on an iOS computer - such as a mac or macbook, but not one of the "touch screen" devices, such as an ipod, iphone, ipad.
I'm afraid this is a sacrifice that is well worth it. I can easily register on behalf of a person that ONLY has access via their ipad. However, most people have a computer they can use and don't even need that.
Since the forum update and addition of this anti-spam measure, the spam posts on this board have dropped to almost zero.
All Cacti are succulents, but not all succulents are Cacti