1. Have you created this yourself or are you using proprietary software? If so, which one?

2. What information do people have to enter to register?

3. Is there a discussion board/forum that they can post to, where they can all see every post?

Basically these bots are designed to attack bulletin boards and discussion forums and they are unlikely to be able to handle a custom format that is different from that supported by the proprietary software.

They are not interested if there isn't a forum for all to see and contribute to.

There are lots of ways of stopping bots, but they depend on your particular setup. Things like IP address blocks, forbidden words, access times, pre-moderation/validation and so on.

Any idea of the number of members and amount of traffic that are expected?