"arguing with teenagers is a zero-sum game"
I love this line.
Anyway, I completely understand and respect Jason Robert Brown's opinions and I admire that he has managed to make a living writing music and selling sheet music. That said, being a musician and composer who has worked on countless musicals, I've seen the flip-side of this equation. I have seen producers lose their shirts because of the prohibitively high cost of obtaining the rights to full scores (notably more than $4.00 a song). Simply put, it's not pretty.
Brown is right to defend his rights and defend his trade, however I think there is room for modernization in the copyright model employed by broadway show rights holders. Personally, I am a fan of (and often employ) creative commons licensing. I like the idea that if you're not going to make any money on my material, I won't either. This gives me and my material exposure (and hopefully a little popularity) and doesn't lose me any money. If, on the other hand, you're going to make a killing using my works, for sure I want a piece of the action. Most broadway shows do work on a sliding scale, however the scale does not slide low enough to accommodate most amateur productions.
The other issue with the current copyright model is that it is only concerned with short term gains. The actual term of a copyright before it is released to public domain is obscenely long. Obviously, this is to benefit the publishing houses. This means that even decades after a work is published, it can be extremely difficult to obtain the rights to put on the production. This has been shown to actually diminish the popularity of works since it is easier for amateur productions to find older public domain works, instead of fresher newer works (hence the continued popularity of Gilbert and Sullivan). Releasing works into the public domain (after the initial run) can help to boost the authors popularity and prevent them from dying in obscurity as so many composers do.