Let me provide another viewpoint: many people don't understand the GPL, and any criticism of it elicits a knee-jerk reaction.

I've been in discussions about problems with the GPL in several companies already. The real problem is not (as most people tend to think) the requirement to provide source code and the rights to modify and redistribute it. The problem is the patent claim landmine that is considered to be dangerous by many lawyers (see GPLv2 Section 7, LGPLv2 Section 11). I don't want to go into excessive detail here, but in brief: the danger is that you might have to immediately stop redistributing the software if you become aware of a patent that would restrict the rights provided by the GPL.

A library project which is under GPLv2 or GPLv3 gets immediately rejected in many (most?) commercial settings. Note that I'm not judging here — just stating a fact. We ourselves reject a lot of interesting options because of licenses and I know most other companies do so as well.

Now, LightTable is not a library project, but I can imagine how companies would like to bundle it, or bundle a modified version of it. The moment you "redistribute" it, the GPL applies, and if you build a business on this software, that business might have to suddenly fold some day because of patents.

Please don't respond along the lines of "you might get a patent lawsuit anyway". Yes, you might, but then it's a lawsuit, which you can defend against.

Please understand that the license change is a really big deal for some people.