There are several connectors between Python and MySQL under various licenses. Here are some of the more popular ones:
- MySQL Connector/Python (the "official" connector) is dual-licensed the same way as MySQL itself: you can choose a commercial license or GPL-2.
- MySQL-python is dual-licensed under GPL and the more permissive Python 1.5.2 license (see below).
- PyMySQL is MIT-licensed.
If you decide to make the server code GPL, does the client also have to be released under the GPL? This is a difficult question and depends on whether the server and client should be considered two parts of the same program that just happen to communicate over the network, or if they're two separate, but interoperable programs. See Can I commerically use GPL licensed software on my server if I am only distributing the client software?
Original answer that explained the dual license of MySQL-python:
The README that comes with the MySQL-python-1.2.3 source states this in the License section:
License
-------
GPL or the original license based on Python 1.5.2's license.
I'm not sure what exactly the "original license based on Python 1.5.2's license" is, however Python 1.5.2 was released under a modified CWI license, which is a permissive non-copyleft license:
Copyright 1991-1995 by Stichting Mathematisch Centrum, Amsterdam,
The Netherlands.
All Rights Reserved
Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted,
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in
supporting documentation, and that the names of Stichting Mathematisch
Centrum or CWI or Corporation for National Research Initiatives or
CNRI not be used in advertising or publicity pertaining to
distribution of the software without specific, written prior
permission.
While CWI is the initial source for this software, a modified version
is made available by the Corporation for National Research Initiatives
(CNRI) at the Internet address ftp://ftp.python.org.
STICHTING MATHEMATISCH CENTRUM AND CNRI DISCLAIM ALL WARRANTIES WITH
REGARD TO THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL STICHTING MATHEMATISCH
CENTRUM OR CNRI BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL
DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
PERFORMANCE OF THIS SOFTWARE.