I'm going to merge this into T4431, because it overlaps with a more general request ("it should be easy to make a project that has a common set of columns"). It's not precisely clear what this will look like yet.

Fair enough. In the mean time, I'll patch this piece of code:

public function getDisplayName() {
  if ($this->isDefaultColumn()) {
    return pht('Backlog');
  }
  return $this->getName();
}

Oh, sorry, I misunderstood: I thought we already let you rename it, but you wanted to change the default name for new columns.

We don't actually let you rename it at all. We should. This can stick around.

(T4431 will solve the other problem.)

In T5101#6, @swisspol wrote:

Fair enough. In the mean time, I'll patch this piece of code:

You might be able to add your change to config/group/translations/ instead of maintaining a local patch.

Indeed it works, thanks!