The GPL may be a community-building signalling device, but it is also a confession of fear and weakness. To believe that it matters, you have to believe that you live in a Type A universe where closed-source development is such an attractive proposition that you have to punish people for trying to move to it.
Rather than sell software licenses for static, hard-to-customize software products, we're informing libraries about the benefits of open source, enabling them to make choices about how best to provide their communities and staff with better technology services.