In the process of updating the last public release to 1.4.6 I found that not everything transitioned smoothly.
A few functions/variables that Mystcraft used became inaccessible. I have pushed a PR to Forge, but don’t know how one of the newer systems works so I can’t do it quite right. I’m sure Lex or cpw could fix it, but Lex isn’t handling PRs right now and cpw hasn’t been online very frequently of late.
I will attempt to learn this new system so that it can be merged in directly, which will hopefully get it in sooner.

Again, this release will not include Pages or Modifiers or any of the newer content. It is an update of the last release, built on 1.4.6, with some bug fixes and such.

Hopefully the release will be soon, but I can’t say when.