Open-source but not GPL zcode interpreters?

What’s the best codebase that isn’t GPL?

Fizmo is not GPL. It uses curses for I/O.

Bocfel is GPL, but it’s a single author effort - you could ask Chris Spiegel about a special licensing arrangement. It uses Glk for I/O.

Fizmo seems right. (Although I’m still open to suggestions.) Thanks.

(I want to Glk-ize it, and Bocfel is already there. Hm. Well, options are good.)

There is a Perl offering: ‘rezrov’ - Perl does have a non-GPL licensing option, their ‘artistic licence’ as they put it, but I have no clue what that means. Additionally, I cannot speak to rezrov’s capabilities…

Artistic License is Perl’s open-source license, which is good for the purposes of this question. Unfortunately I’m looking for C, not Perl. (I forgot to specify that – sorry.)