John L. Ries wrote:

Such a policy would seem irrational to me, as I fail to see any real benefit to the project, but it's possible I'm misunderstanding something.

I didn't say it was policy. I said it has an influence.

Many of the developers think that GCC can and should compete on technical merit alone, but a there are those who think that the design needs to protect the license. Sometimes decisions lean in one direction, sometimes they lean in the other direction. Both these groups have an influence.

The decision of whether or not to introduce a plugin interface was certainly made at the highest level at the FSF, so you may want to consider than a matter of policy. But many decisions are made further down and they shouldn't be considered matters of policy.

There was another incident many years ago where a developer had created a GCC to JVM translator or vice versa and was about to donate his code to the FSF. Richard Stallman was outraged and he trounced this poor guy in public, asking him to destroy his code so it would never leak anywhere.

Clearly there is an influence of the school of thinking that says design has to follow the license. I wouldn't call it policy, but the influence is there.