TeX-other-free

The TeX Catalogue License Definitions: OTHER-FREE
Licenses not clearly (or uniquely) defined, but believed free.

This license statement is used in two distinct circumstances. Either
the software is covered by a license that does not fit into any of the
"formally" specified categories, but the CTAN catalogue team judges it
usable by most users. Otherwise, the software consists of distinct
parts to which different (free) licenses apply.

While use is probably safe, each potential user should check the
software's license statement (or statements) before using the software.