Nightbringer

I had both. Parents got us a 7800 for Christmas one year and one of our Aunts got us an NES either the next year or the year after. I don't remember when we got them, but the 7800 had the larger, original box and I remember drooling over the games on the back. Once we got an NES the 7800 got put away and only taken out once or twice after. Both consoles disappeared sometime in the 90s when I was in college. I was pretty much in to PC gaming and didn't buy another console until I got a used PS2 slim!

Is the 2600 particularly sensitive to power? I've taken a couple random 9V power supplies (switching and linear) and put a 3.5mm jack on the end without any noticeable problems.

Have you only tried one cart? Looks like a dirty cart or cart slot to me, but since you've cleaned it, I'd try another just in case.

It's illegal anyway. Adding a copyleft license doesn't make it any more illegal than a non-permissive license.