Can I contribute a package dependent on a non-FSF package?

[Tim Van den Langenbergh]

Hello,

I've quickly thrown together Babel bindings for Raku[1][2].

Unfortunately the raku-mode package does not have its copyright assigned to
the FSF, and I'm using the comint mode from that package.

Can anyone tell me the best way to proceed? I could blatantly copy over the
comint interaction code if needed. Although if possible I would like to keep
the raku-mode requirement.

I would be most appreciative of any help.

Vale,

-Tim Van den Langenbergh

[1] Formerly known as Perl 6.
[2] Code available at: https://github.com/tmtvl/ob-raku