@asa @sun All GPL project are by nature decentralized as it doesn't require a central authority.
People can gladly contribute to the main linux kernel if they wish AND if they are accepted.
If they are not then they are free as in freedom to fork and do the changes they do.
Such is what is for example the linux-libre project.
And it doesn't stop the main kernel people to bring back peaces made in the linux-libre fork into the main kernel. as the GPL allows sharing.