On 1999-10-13, someone posted to the userfs mailing list (linux-userfs@vger.rutgers.edu) that they had a 'tapefs' and an updated userfs. It was at http://www-internal.alphanet.ch/archives/local/alphanet/linux/drivers/userfs/, but was only accessible to people using certain browsers (evidently for political reasons outside the control of the guy who posted it). This is a mirror accessible to everyone.
I updated it on 1999-10-13, and don't plan to update automatically in the future.