I did and it was the best career move I ever made. My undergraduate degree was in a non-tech area. I spent the first 2 years of my practice at an international law firm doing banking and finance law. When I couldn't take it anymore I went back to school to get a formal education in Computer Science. At the end of the program, I had multiple offers to be an IP lawyer.
OSS is so pervasive now that every single company must take it into account when doing any type of software project. Companies that can effectively use OSS (and have good legal counsel to help them be effective) have competitive advantages.
I am not saying your friend has to go back to school. Knowing the basics of software engineering is critical however to be an effective attorney in the open source area. You must also have good knowledge of copyright, patent, and trade secret laws. I do a lot of work in the compliance area (making sure my clients are not violating open source or other licenses from upstream providers) and I cannot even begin to recount how many times my legal opinion to a client has depended on the specifics of the architecture of a piece of software.
A career in law is too difficult to spend it practicing in an area you do not love.