Actually quite a lot. Starting in 2015 they worked on BOLTS, which was a uniform set of rules that different companies had to follow to operate on the Lightning protocol. Rusty is in charge of those to this day. He later joined Blockstream and developed much of their version of Lightning, but I think he's got his own dev lab now. Various features in lightning wallets you may have used were his ideas.

In the 90's he did a ton of work on the Linux Kernel, so most operating systems around the world have his ideas implemented in them right now too.