Well, there is nothing to say you have to use the Abandonia Minecraft server.
I did notice that, when you connected the other day, Riccso, that the other person who was on there was disconnected as you joined (that could've been a coincidence and them quitting however...).
If you keep the hacks blocked, then I don't see a problem.
I think that the new version of the client you can get from
World of Minecraft works with version 0.30 of Minecraft (the other ones aren't compatible with this version) and has the option to turn the hacks off.
You can also do it if you run the game through the Java console, rather than in your web-browser.
I've no idea how to do this on PC, but you can run Terminal (unix or MacOS) on Mac - perhaps you can find out over at the Minecraft Forums..?
There's only a few weeks left of this competition.
We'll decide on the winners and announce them (hopefully in the magazine, if it is ready then) in the New Year.
So
GET CRAFTING PEOPLE!!! 
