A wee bit late on this thread. But I personally know Josh (Synthboy+ Dev) and he is a great guy.
I very much dislike the bs surrounding projects like this. I understand your concern on legality but I don't understand everyone's very opinionated petty stance on the synthboy+. I have used the synthboy+ and it is a lot of fun. For some awful reason everytime I play live 19 different things go wrong with my gameboy. After playing around on this synthboy+ I may just purchase one. Because It feels safer and secure. Arduinoboys feel so temperamental to me. (I know they don't have to be, but most everything that touches a gameboy becomes fragile)
Chiptune is a niche genre already!, so something like this doesn't deserve your harsh sentiment. There is only a small group of us out there, so I believe we should support each other in our endeavors. If purist elitism persists, the scene is just going to fade away.
Oh and Most of you have the same point of view as well, which isn't healthy discussion.
I am going to support Chris and Josh because they are good people, trying to help the scene move forward.