Due to the recent surge of interest in porting ZFS to the Linux kernel (if you are in the mood to read dozens of messages, see this thread, the follow-up, plus this one and one more), I'd like to offer my view on things.
IMAPFilter is a mail filtering utility. It connects to remote mail servers using the Internet Message Access Protocol (IMAP), sends searching queries to the server and processes mailboxes based on the results.
SwitchPipe is a proof of concept "Web application server" or, more accurately, a Web application process manager and request proxy. Backend Web applications are loaded into their own processes, making SwitchPipe language agnostic. HTTP requests are proxied at the TCP level using information extracted from the headers to establish which backend application is being demanded.