Hello 32,
Harmony currently can not match the in-betweening abilities of CACANI. Like it was mentioned, CACANI doesn't require any type of rigging. You can work by using multiply layers within a "Cel" or can just not used them and draw everything in a single Cel or layer. Is a matter of taste, but most traditional artist will try work on single layer or very limited amount. No rigging what so ever is needed, minimizing the technical for artist. Tweening results are different than in-betweening, although they can look similar.
The software is not for sale due to production trials. We are making sure CACANI is production ready, before it moves for commercial use. Harmony could work together with CACANI since Harmony does not posses the strengths CACANI focuses on, (no need to replace one software with another). And the same can be said about CACANI not having Harmony's strengths such as node composting, forward kinematics, inverse kinematics, effects, etc...
There is no other software in the market that can currently match CACANI base on the strengths it focuses on. Most 2D software do not focus on traditional toolsets anymore (they make some additions but very little), but they focus more on puppet style (Flash style) tools. This have made them stagnant on their offering when dealing some professional studios. Precisely because of this CACANI is getting more attention.
Now that said, Toonz, Toon Boom, TV Paint, Anime Studio and others are fantastic tools if they can offer what the artist is looking for for their projects.