I've done that, and my most personally profitable years were doing that, billing $125/hour the last year I did it (this was eleven years ago), and working slightly more often than I wanted to be. There was a lot of travel, as my particular specialty was something that was needed by companies with very large websites, but not by many others, which I suspect is gonna be true of most of the "which people pay good money for skills in" projects. Being a contractor has most of the same disadvantages of having a real job; maybe pays a little better, and maybe you work a little less because of it. But, it has some additional negatives that I found made me unhappy.

I haven't gone back to contracting not because it isn't profitable, but because it isn't what I want to do. I want to build things, not merely install and configure software (even being really good at installing and configuring complicated software leaves something to be desired in the "job satisfaction" category).

Anyway, I've been making my living on Open Source software for approaching 20 years, through two different companies, and a half dozen pivots and business models. I'm not making statements out of lack of knowledge of the topic.