I've purchased them in the past on G11 or G16 (both dwarfing Cornell rootstocks) from Cummins. Liberty's a popular variety right now and I can't imagine that you'd have too much trouble finding them at some other nurseries.

I don't know what it'd be like on truly dwarfing rootstock, but Liberty can be a bear to control on semi dwarf. But the apples are great (I think) and, as Harvestman puts it, it's a fruit machine.

I certainly agree about it being a Fruit Machine. Even though it's not in my best spot, my Liberty is my most reliable producer, consistently putting out large amounts of apples year after year. And, I'm happy with the flavor. -Glenn