This is the bugfix release for 0.10. Thank you for your patience, I had a lot of things to tend to. :)

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 goes in the mods folder.

If you are still lost after 0.10, check out Direwolf20′s Mod Spotlight!

Download: [1.4.7] Mystcraft Universal 0.10.1.00
Check the Mystcraft Forums for updates and the change log.

Enjoy!