A GreenfieldProject (incorrectly named GreenfieldApplication here) is one with no legacy code. You can start from scratch using state-of-the-art principles, yet you are expected to hit a business goal in short time.

A BlueskyProject starts from less-than-scratch. It intends to push the state-of-the-art. Example: WardsWiki. You collaborate with your business side (if any) to discover business goals as you go.