This is being addressed by this bug:
Bug 25854 - Need to better differentiate free/busy status from participant status
In the meantime, if you made a change the javascript *source*, you'll have to redeploy the webclient via ANT:
under <src>/ZimbraWebClient, run "ant prod deploy"
If you installed from a pre-built binary, you'll have to unzip the gzip package file for calendar (since you modified ZmCalColView.
js). I think the one you'll want is calendar_all.
js.zgz (or something like that). Once unzipped, make the change, re-gzip it (but be sure to backup the original in case you fubar everything) and restart jetty.
IMO, you're better off voting for the above bug and waiting for the 5.0.5 release.