Originally Posted by lar
If you already own DKS, you'll be upgraded for free to Dev Cut (at least that's the intention, we're still working out the details but they *should* be worked out by the time the digital versions of Dev Cut & Anthology go live.

As far as Dev Cut is concerned - it includes the full DKS, but then also comes with a separate executable that allows you activate the Developer Mode. Additionally, it also includes a documentary & the treasure vault, a folder containing all kinds of goodies like milestone videos & design documents.