Google developed linux cgroups. IBM developed linux namespaces. Docker developed a completely new application runtime and delivery system, built on cgroups, namespaces, aufs, and tar. This required lots of original design and engineering work. Prior to Docker, there was no runtime contract for distinguishing the portable application bits from the non-portable host-specific bits. You just got a machine, and then had to provision, configure and templatize it - then upload application bits into it yourself.

All three companies contributed significantly to the modern container stack. As the co-founder of Docker, and someone who spent 10 years toiling away at container technology before it finally became cool, I wish people had more appreciation for the amount of engineering and design work that went into that. Google and IBM contributed the primitives that made Docker possible. But Docker made genuine contributions of its own.