Best response to that might be: “Because they could.”
Guess that someone figured that the URL was there and nobody in Columbia wanted it, so this is who owns COLUMBIABOROUGH.COM according to http://www.betterwhois.com:
Domain Name: COLUMBIABOROUGH.COM
Registrar URL: http://www.godaddy.com
Registrant Name: E J White
Registrant Organization: White Enterprises International
Name Server: NS41.DOMAINCONTROL.COM
Name Server: NS42.DOMAINCONTROL.COM
Google White Enterprises International and you'll be directed to this Website: http://www.wrightsvillerentals.com/ H-m-m-m.
Google EJ White Wrightsville and you'll come to this picture at a topix.com Webpage:
The cutline beneath the photo says, “Hey, how about that nice new rental location at 108 N 2ND street? Not only can you get ALL the new releases, including some you can’t get elsewhere, you can also rent Borough Council Videos there!”
So, what’s the path? Dunno’ … but http://www.columbiaborough.com has left the building for Wrightsville.
Here’s a related article on buying and selling URLs.
"Buying up domain names in order to turn a profit"
Columbia news, views & reviews 
E J White has been a wanna be business person since he was a kid. Never had any great success. Look at the old gas station at 5th st and Lancaster ave in Columbia.
Why is it that Columbia Borough never registered their own domain name ?
That’s a question that ought to be directed to the folks citizens elected to captain the good ship, Columbia. Promotion and setting plans for domain ownership is the realm of “community development.” And URLs are selling now for 50 cents and up.
Perhaps the “captain of this great ship ” should take a stroll across the river and offer the guy a little wad of cash for the domain – it belongs here