Eda-tools is a project mainly written in SHELL and PERL, it's free.
KiCad visual schem diff, among other things!
This is a collection of utilities for Electronic Design Automation:
boom: a BOM-processing system. Note that the core scripts of BOOM are at http://svn.openmoko.org/trunk/eda/boom. The material here builds upon them.
dsv: data sheet viewer. A simple but efficient system for caching data sheets and displaying them with xpdf from command line.
fpd2pdf: convert a set of footprints (made with FPED) into a reviewer-friendly PDF.
fab: set of tools to convert/generate files for fabrication
mlztx: set of tools to copy text across layers or across text fields in a layout, e.g., to place a version number at several locations
schhist: a system to walk a KiCad project's git revision history and generating Web-browseable graphical differences of the schematics.
swpcmp: swap components in a layout
Each utility can have its own licensing terms. They're specified in the respective directory or in the file itself.