Am 13.10.20 um 23:27 schrieb Reinhard Kotucha:
>   > FWIW, I suspect Thanh would not have a problem with allowing use of
>   > those primitive implementations under CC0 or any other license terms.
> AFAIK it's under GPL because it contains libraries from xpdf and maybe
> a few others which were already under GPL.

which is fairly irrelevant isn't it? If Thanh has written code for, say, 
\ifincsname then he can license this code the way he like on its own. If 
combined with xpdf libraries in a pdftex binary the combined result may 
have to be GPL (though even this is debatable) but if on its own it can 
be definitely licensed differently.