I think you may be confusing a product with a suite here.
ObjectDock is a product which gives you a OS X like dock on your desktop.
ObjectDesktop is a suite of products which includes Start8, ModernMix, Fences 2 etc (but not ObjectDock as it happens).
Of the products in ObjectDesktop the following are Win8 compatible :
Start8, ModernMix, DeskScapes 8, Fences 2, WindowFX 5.1, Decor8, IconPackager, Tiles and IconDeveloper are Windows 8 compatible. Of the main apps only WindowBlinds (and SkinStudio due to it needing WindowBlinds to be installed) do not currently support Windows 8.
You get a discount for having one or more of the products in ObjectDesktop. I believe the current upgrade from a standalone product is $34.95 and this can be found on the ObjectDesktop purchase page. You will need your account details in order to order the upgrade.