I just think that he is just enjoying his millions and taking time off coding. There are other miners right now that people can use. Maybe if ETH forked to a different algo or if mining was "extremely profitable" again he would start to coding his software again but right now you see how it is. It was profitable about 2 weeks ago, people powered up their rigs and now profits are half of what they were since then assuming average power of $0.10/kwh.

He has made extreme profits if he held his ETH and sold when ETH >$1000. His miner was very popular before BTC and ETH broke $1100 and $20 respectively. Probably traveling the world right now or sailing across the sea on his yacht.