Would suggest some indication that tiles are being loaded after you select a tileset. Also, I presume the collaboration feature's not there yet?

EDIT: Oh wait, I totally misread your posts, you never announced a collaboration feature. Bummer.

In any case I would suggest thinking twice about replication offline JCS' layout for web use. I don't know what the goal of your app is, but offline layouts don't necessarily adapt to online ones well. Would suggest rethinking how JCS should work, so that a webJCS has added value above the regular one (ease of use, features that you would only be able to offer on the internet (for example: integration into existing information places, collaboration)