OpenBSD-4.6/usr.sbin/popa3d/LICENSE

You're allowed to do whatever you like with this software (including
re-distribution in source and/or binary form, with or without
modification), provided that credit is given where it is due and any
modified versions are marked as such.  There's absolutely no warranty.

Note that you don't have to re-distribute this software under these
same relaxed terms.  In particular, you're free to place modified
versions under (L)GPL, thus disallowing further re-distribution in
binary-only form.