Once again, I end your waiting. This time the wait was short.

To recap: there is only one download (found at the bottom of this post); This file is the universal install for client and server; it no longer goes in the jar.
Mystcraft now goes in the mods folder.
This release requires Forge 6.0 or higher.

Download: [1.4.2] Mystcraft Universal
Check the Mystcraft Forums for updates and the changelog.