Yes, I have compiled and use one. I'll upload it to ftp.ph.kcl.ac.uk.

If all the mail in the POP box is for one user, you can just append it
to their mailbox. Mine isn't (all mail sent to
<anything>@hayward.u-net.com goes to one POP box), and I have yet to
find a satisfactory way of distributing it locally when it arrives...