Why not plug into Jazz2Online somehow to get the tilesets? That way you only get approved ones.

I'm interested in testing this - I'm an experienced webdeveloper so I might have suggestions.

What I'm wondering is, how is it collaborative? The problem with AJAX isn't keeping a connection open (the point of AJAX is that it doesn't) but that if you want realtime collaboration you need a huge amount of requests/updates to the server. That was what broke my tool: it used one request per tile. That'd bring the server down in no time. Browser protection prevents you from opening a connection using javascript to another client. How is the level editor collaborative if it only uses AJAX while saving? Is it collaborative the way google docs is? You save a file, someone else can open it?