The source code under src/ucsc comes from Jim Kent's source utilities.
Any usage of this code should follow the license restriction.

The following lines are taken from README of Kent's utilities.

This directory contains the entire source tree for the
UCSC Genome Bioinformatics Group's suite of biological analysis
and web display programs as well as some of Jim Kent's own tools.
All files are copyrighted, but license is hereby granted for personal,
academic, and non-profit use.  A license is also granted for the contents
of the src/lib, src/inc and src/utils and python directories for commercial
users.  Commercial users should contact for access to other
modules.  Commercial users interested in the UCSC Genome Browser in particular
please see