Being the default in Linux distributions may not be the only, ultimate goal. I agree that it is probably too late for Fedora or Debian to change back.
But lots of people are currently running syslog-ng, and others are installing them from source/distribution packages, yet others are including syslog-ng in their products.
And for them this license change may be reassuring.
Being late is always better than never in my opinion, and doing the right thing with regards to making a living from free software is not an easy ride. Getting it wrong and learning from the mistakes is at least as important as doing it right from the beginning.