I don't know if I believe that Guido Van Rossum has to spend 50% of his time on not making python better, but perhaps it's true. Isn't he at dropbox now as well?
It's not clear to me that Guido actually wants to spend more than 50% of his time on Python. Stuff like the async stuff he's bringing into Python come from his time spent developing things with Python during the other 50%.
Also, is Python necessarily his unicorn now? It's certainly not the same as a project that he conceives and creates - it was a long time ago, but success changes that.
He currently works at Dropbox, and it looks like he took his 50% deal with him: "In January 2013 I joined Dropbox. I work on various Dropbox products and have 50% for my Python work, no strings attached" [1]
I'm going to guess that GVR wants to spend 50% of his time on other things. If you're a language designer and you don't spend half your time programming to core business needs, you risk isolation and your quality of inspiration will go down.
One of the reasons why Clojure is great is because Rich Hickey actually goes out there into the enterprise and has put a lot of thought into making it an extremely practical language in a wide variety of business settings, without compromising on the things that actually matter.
