I'm not sure you're wrong. I was under the impression that contributors retain copyright over their portions under GPL.
This would require the copyright holder of the larger piece to get permission from all contributors before releasing under a different license, and I thought Ubuntu's CLA with Mir was to ensure they weren't trapped by this.
This would require the copyright holder of the larger piece to get permission from all contributors before releasing under a different license, and I thought Ubuntu's CLA with Mir was to ensure they weren't trapped by this.