I started to consider the reasons why open source vendors select the GPL after ESR wrote:
The GPL may be a community-building signaling 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.
The first reason has to be the big-bad Elder Companies. It's no surprise that Elder Companies prefer more permissive licenses such as the Apache license. OSS startups fearing that their work will be hijacked by a larger vendor tend to select the GPL as a result. The validity of this fear has been called into question by the success of Oracle's Unbreakable Linux. Or imagine if MySQL had used the Apache license. Would Oracle, Microsoft, or IBM (or others) have been able to use MySQL's intellectual property to compete against MySQL? Well, in theory, yes. In practice, just imagine the community uproar against an Elder Company that tried to fork MySQL. Using the GPL for fear of Elder Companies is unfounded.
The second reason to use the GPL is to encourage customers and partners to pay for the open source software in question. Let's only consider the situations where the customer or partner is seeking not to pay for the OSS.
Does the GPL encourage payment from a customer any more than the Apache license? I'd argue no. Very few customers create applications that are distributed outside of their walls. Hence, there is no trigger for the viral nature of the GPL. A customer could equally choose to use GPL or Apache licensed software without paying the OSS vendor.
Does the GPL encourage payment from a partner any more than the Apache license? In this case, yes. The partner must choose to pay for a commercial, non-GPL license or choose to license their own product under an open source license. Since the latter is not the preferred route for ISVs/SIs, especially regional ISVs and SIs, the GPL does encourage payment more so than the Apache license would. But there's a catch: The GPL would force this partner (that doesn't want to pay or open source its product) to look at non-GPL alternatives. When this occurs, the OSS vendor has lost a partner and end-customers delivered through this partner "forever" (as long as that is in the IT market).
The third reason is that the OSS vendor intends to leverage code from third party GPL projects. Considering the amount of GPL projects out there today, this is a pretty strong reason for startup OSS vendors to select the GPL.
For me, reason no. 3 is, at this stage in the maturity of open source, the reason that the GPL will retain it's dominance in the industry. For better or for worse.
Follow me on Twitter at: SavioRodrigues
p.s.: I should state: "The postings on this site are my own and don't necessarily represent IBM's positions, strategies or opinions."