licence for Contrib/System?

I'm looking at the source code for preparing an nsis debian package, and I note that there is no licence for the code in the Contrib/System/. Anyone know what licence nsis is distributing this under?

The NSIS license states:

This license applies to everything in the NSIS package, except where otherwise noted.

halibut, for example, is GPL. Contrib\System is licensed under zlib.