Those of us who pre-ordered the Delving Deeper boxed set have started receiving the no-art PDFs, prior to the shipment of the actual sets. I've received Volumes I and II so far; Volume III is expected tomorrow. I've done a quick read-through of the character creation section, but I plan on doing a more thorough reading, followed by a review.
I've noticed a few significant differences from the LBB rules, but it seems to be pretty close, which suggests strongly that Liber Zero, as a straight-up OGL retroclone of the LBBs won't be necessary. Instead, I will probably re-focus on putting LZ together as a non-OGL, Creative Commons ruleset that de-emphasizes resolution mechanics (allowing you to substitute the ones you prefer) and focuses instead on the rules around the mechanics, as well as on the building blocks of things like monsters and spells. The final product will actually be more useful for those already committed to Delving Deeper, Swords & Wizardry, Labyrinth Lord, or the official rules, as a way of expanding or clarifying those rules.