Actually, I'm pretty sure that's posted somewhere. The level wasn't remade, it was just hex edited. I was really simple too. Come to think of it, I think there was a post written somewhat like a tutorial so beginners could try doing things like that themselves with freeware disassemblers and hex editors. It probably could have been done within half an hour even if you had no idea what you where doing, and needed to download the software.
Edit: I can't seem to find those posts anymore. Maybe they're gone. They don't seem to be in the archive either.
Anyways, if you wanted to do it yourself, you'd probably use OllyDbg, check the names table (Ctrl+n, when you have the disassembly window active), and find the decorated name for GoEden, or GoPlymouth. They'll have a bit of junk on either end of the name. If you follow them in the code window, you should see a CALL <address>. Write down the addresses, and exchange them. (There will be one call for GoEden for your colony, and one call to GoPlymouth for the AI colony, so make sure you look up both of them). If you hit space (or maybe most other keys) with the line highlighted, it should popup a window with the current instruction and allow you to enter in a new instruction. Just change the address portion of it. The code bytes will change, and probably be highlighted in red.
You might need a hex editor to make the actual changes and write them back to the file. In which case, write the new red bytes over the old bytes. You can always do a search for the old bytes to try and find the right location in the file. If you've already overwritten the old bytes in OllyDbg, then you can use backspace to undo the changes to see them. Also, make sure the found locations are unique. You don't want to overwrite the wrong place. If it's not unique, then search for a few extra bytes around the desired instruction until it is.