Honestly there are plenty of open source tools out there that will allow just about anyone with a little programming knowledge to make basic cheat utilities for UO. This information has all been publically available for quite some time. You can't open Pandora's Box when it is already open. How do you think most of the emulators and third party utilities got started to begin with? They all had a wealth of information to build on.
There will always be cheat programs and UO will always be vulnerable to certain types of cheats and exploits, unless they totally redesign the way UO functions and the way the server and client work. And UO isn't alone. EQ has cheats, WoW has cheats, Diablo has cheats, I bet even Asheron's Call has cheats. There are very few games that are cheat proof. UO alone has had Injection, which morphed into UOE and its various incarnations, as well as Speedhack, IRW, UOCH, EasyUO, and many others. You can do all kinds of tricks that are undetectable server side, like those patches that make trees and and blocking obstacles easier to evade by using a statics file that removes leaves and house walls and roofs. This doesn't even include utilities that aren't UO specific, like mouse and key macroing programs. Some people consider UOAssist and Razor to be cheat programs.
But I think most people don't want to cheat, and especially on a small server like most of us have, cheaters are pretty easy to find and weed out. Just do some profiling of your server through reports (like tracking player wealth and numbers and types of items) and random observation of your members. Most people who cheat are pretty greedy and stupid about it.
P.S. But back to the topic at hand - regardless of the reasoning, its up to the program's author to decide if he/she wants to release the source. Respect their wishes and be glad we have the utility in the first place.