Re-using copyrighted code

[Malte Forkel]

Hello,

I have written a small utility to locate errors in regular expressions
that I want to upload to PyPI.  Before I do that, I would like to learn
a litte more about the legal aspects of open-source software. What would
be a good introductory reading?

Plus, I have one very specific question: In my package, I use modified
code from sre_parse.py, which is part of the Python release. That file
has the following header:

#
# Secret Labs' Regular Expression Engine
#
# convert re-style regular expression to sre pattern
#
# Copyright (c) 1998-2001 by Secret Labs AB.  All rights reserved.
#
# See the sre.py file for information on usage and redistribution.
#

The referenced information is missing in the version of sre.py that
comes with current versions of Python, but I found it in the archive
http://effbot.org/media/downloads/sre-2.2.1.zip. It reads:

#
# Secret Labs' Regular Expression Engine
#
# re-compatible interface for the sre matching engine
#
# Copyright (c) 1998-2001 by Secret Labs AB.  All rights reserved.
#
# This version of the SRE library can be redistributed under CNRI's
# Python 1.6 license.  For any other use, please contact Secret Labs
# AB (info at pythonware.com).
#
# Portions of this engine have been developed in cooperation with
# CNRI.  Hewlett-Packard provided funding for 1.6 integration and
# other compatibility work.
#

Now, how am I supposed to deal with that? Ask Secret Labs for some kind
of permission? Leave it as it is and add my own copyright line?

Malte