This is not an issue with CraftStudio. He's using a mod (DecoCraft2) which requires another mod (PTRLib) to work. He doesn't have that installed, so it crashes. Installing PTRLib should fix this.
Reminds me that I once had to download a mod from 9minecraft because the original, official host was long, long gone. And I wanted to examine the source code.
I still feel dirty. *shudder*
I don't even like the TheDiamondMinecart. I think he's stupid and rode to fame on a wave of asshat 10 year olds. The fact that skydaz is part of him just makes me repulsed from it even more. I've never once used Skydaz and don't intend upon doing so. If you need an installer to do any of the things listed on that website you should get off the internet and grab a creeper plushie because you're 7 years old.