Pipcard: Unfortunately, I'm on vacation currently and don't have the correct version of minecraft to get on the server to add you. I'll see if I can dig it up, though. Remind me next Monday if I haven't done it by then. Sorry!
As for the walls/towers west of the commune, that's been there since the dawn of time, and actually predates the current block logging, so I can't see who it was. When I get back home I can check the old block logging db to see who it was, but that structure has been in its current state since before the initial End expedition shortly after the new world was created, so it's safe to consider it abandoned.
Given that it's just a couple block high walls and towers without even a second floor, I don't think it's a problem to take over the project. If the original builder shows up, I'll happily reimburse them the materials from my own stash and help them set up something similar elsewhere.
If the structure was closer to completion and represented more than a few minutes of work I'd be more hesitant, but in this case it's just the barest outline of a structure. It's also not like the location is anything extraordinary, either--just a normal plains near a coast, which is fairly common.
TL;DR version: Go for it, Jeff.