OO programs and procedural programs
The OOUI interface assumes, that the highest-level programming design approach used for the client application is "object-orientation" or transformable into object-orientation without information loss.
For other design approachs, new interfaces with the same general concept like OOUI descriptions, but different semantics, should be created, if it makes economically sense.
Examples for other design approachs might be AI based systems. They may use OO, but not on the highest level.
OOUIs targets at all application types, be it tools, office applications or 3D games.
However, applications, which don't have to render by themselves, gain the most from OOUIs, because they can be used in nearly every environment. Examples for such apps include mail user agents and file managers.