Confused: Reef-Pi or Robo-Tank Software?

[rothy]

Hi, I got excited reading about Robo-Tank and have been reading about reef-pi and watching videos.  

Now, I'm reading about Robo-Tank 6.0 which is....different software?  Obviously it runs on Robo Tank hardware....but will all robo tank hardware run reef-pi? 

What is the difference between the two software packages?  Why is Robo-Tank being developed when Reef-Pi seems to have been the software used when Robo-tank first started? 

Thanks!