ERFA has received explicit permission from the IAU SOFA Board to re-license
and re-copyright ERFA from SOFA. The email providing permission is shown here:

> The IAU Standards Of Fundamental Astronomy Board approves the
> relicensing of a changed SOFA library by the NumFOCUS Foundation to use
> a "Three Clause BSD" license.  The changed, relicensed version shall
> differ from the SOFA version in that all function names shall change to
> use "era" as a prefix in place of "iau", and that the SOFA Board shall
> be removed as a copyright holder in the relicensed version.

> Catherine
> Chair, IAU SOFA Board
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> HM Nautical Almanac Office
> United Kingdom Hydrographic Office
> Admiralty Way
> Taunton TA1 2DN
> Catherine.Hohenkerk@UKHO.gov.uk
> ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^