I have put the 4.1 beta test up at:
Please uninstall and delete the bb-fix-stop-spam plugin. I have included its functionality in the 4.1 Beta test of stop-spammer-registrations-plugin. Download and install the stop-spammer-registrations-plugin and test that.
I am still digging into bbPress. I hope that I can make a seamless version that works correctly for both normal comments and anonymous Forum replies.
Please stop by at http://www.blogseye.com and leave a reply on the forum so I can see if it is generating an errors.