'Almost PD' was a licence popular in the mid-1990s for British public domain software. First introduced by Robot PD, it was subsequently taken up by several more authors.
An 'Almost PD' program had no restrictions placed on individual copying or use, but the author's permission was required before it could be distributed by PD libraries.
The licence is roughly similar to the modern Creative Commons By-NC-ND (attribution, non-commercial, no derivatives) with the caveat that commercial use (typically distribution by PD libraries) would be permitted provided permission was obtained from the author.