I have attempted to contact Tim periodically over the last 18 months at the pobox.com address but without response.

Ask on the DBI users mailing list. I know for a fact that Tim Bunce follows that mailing list, as well as at least a few other DBD developers.

You have a higher chance of a respose, as these people generally prefer to reply in a public forum, where they feel their reply also serves a broader public, instead of just the private you.