[rovr138]

Is it a fee for publication or a fee for reviewing?

Found,

> Once your paper has been accepted, we will confirm your eligibility automatically through the eRights system, and you’ll get to choose your Creative Commons license (CC BY or CC BY-NC-ND).

[specialp]

It is on acceptance almost universally. This is why more selective journals have higher APCs. The overhead of reviewing and processing more papers when less ultimately convert costs money.

[zipy124]

Upon publication almost exclusively.