I've written a blog post, *The Trade-offs of Unpaid Free Software Labor, which is a response to Ashe Dryden's The Ethics of Unpaid Labor and the OSS Community.
Reading the word "gap" made me think of "rap", and I imagined they were composing a song called the Brogrammer's Delight, which includes the lyrics:
I do mean to brag
I do mean to boast
I'm fucking awesome on GitHub with the code I post.
The main hiring decision is made through "homework assignment", discussion around the results and good old interviews. One potential employer uses pair-programming-as-interview like Dryden suggests.
It is disturbing indeed that work on free software is used as a gateway into non-free work. I think if I am going to find a job working on free software I am going to have to create it myself. But then I first need to find the spare time to work on free software, which, as anyone can see (ha!) on my github, gitorious and gitlab accounts, I do not currently have.