Thanks Merton. The problem with things being a "management" decision is that they may not reflect the lived experience of people on the ground. When I lived in Woking, Surrey, I had a Guildford postcode but a Byfleet phone number. Do people living there prefer to use WO, GU, BY, or SU? You can't make a management decision without talking to users.

What happens when populations change? If an area of Dallas becomes a property hot-spot, do you have to reissue all the codes?

Finally, saying the DB is free doesn't answer the question of licencing. There are plenty of free solutions which require payment for commercial usage.

I wish you luck with your endeavour - and hope I am proved wrong.