Wow, I had mistakenly assumed that you couldn't do 0.8 mm BGAs on a hobbyist-level PCB. The solder lands are actually within recommendations.
The author mentioned that this is a test board without much hooked up. That really helps, since not every pin needs to be broken out. On a more complex design with higher pin coverage you'd need more layers to be able to route it all.
This is actually new, OSH Park has made a couple big improvements in the last year or so; it wasn't possible the last time I looked into it, and even then OSH Park was a bit of an outlier in terms of the small process sizes they could do.
I underwrite that wow also, I have fantasies about my own custom FPGA designs, looks that it could be done with garage-like resources following this workflow!
I shared this from Henrik Forsten's blog. It is worth reading all his other articles, too, if you are interested in computer architecture, electronics, programming or math. He has a very wide range of interests.
Nicely done. I did not realize that OSH Park could be made to work with BGA devices. And I'm really impressed he got it into a 4 layer board rather than a 6 or 8 layer board.
It's definitely KICAD— I've had a good experience with it. The OS X port has some nasty crashing bugs, unfortunately, and the library management leaves a lot to be desired. But for basic boards, it's terrific.
One is pretty simple (you just need an Ethernet PHY and a connector with magnetics built in (or connector + separate magnetic transformer).
Two would be harder, because the chip only has one Ethernet MAC built in. You'd need another controller chip and a fair bit of supporting circuitry. But it could be done.
The author mentioned that this is a test board without much hooked up. That really helps, since not every pin needs to be broken out. On a more complex design with higher pin coverage you'd need more layers to be able to route it all.