In case anyone finds it useful, I recently posted an edition of Byrd's "Sing Joyfully" voiced for SATB on CPDL. It's more-or-less hacked together and will surely make a few people cringe, but perhaps someone with more time will come along and find it a useful starting point.

As I wrote on CPDL, "Seeing that there was not an SATB version of this piece in the public domain, I prepared this one. It is a very rough edition based on the organ reduction in the Frank van Nimwegen (SSAATB) version already on CPDL. This edition is in C Major and has some rhythms simplified, for the sake of singability. I hope others who have the time will come along and build on this/correct some of the errors."