The billion dollar figure, at the end of the day, is brand recognition. The actual cost for someone to re-implement all the code, if someone wanted to, is probably $10M? Even then, however it will be a fly-by-night never heard of again project like... rkt.

http://eliot-jones.com:5690/Home/Trend?id=rkt&allwords=true

http://eliot-jones.com:5690/Home/Trend?id=docker&allwords=tr...

I mean heck, here we are 137 comments into a thread about an alternative to docker and I was the first to mention rkt.