As has been surmised in this thread, RedShirt will be used for open testing of whatever changes we have rolling out to Holodeck. The builds we're putting on Tribble are going to stay on Tribble until we're ready to launch F2P.
Anyone who has signed up for being part of public test shards has access to both RedShirt and Tribble.
Tribble should be online later this morning. We're taking care of the maintenance of the live shard first.