What FC for next build?

I’ve now got my first Arducopter heli (TRex 500) flying properly with a mRo R15 flight controller, and am now looking to convert my other TRex 500, which has a scale fuselage. The mRo R15 is not available at the moment, so I’m looking for alternatives, and am looking through the list on the ‘Hardware Options’ page.

There the hardware is grouped under two headings; “Open hardware” and “Closed hardware”. What’s the difference between those two categories, please? And why is RadioLink MiniPix listed, when there’s a strong warning against using it?

Right now I’m thinking of going budget and getting a Matek F765 or F743.