Python's CRT licensing on Windows

sturlamolden sturlamolden at
Wed Oct 25 17:28:13 CEST 2006

On Windows, the standard Python 2.4 distro is compiled with Microsoft
Visual C++ 2003 and is shipped with msvcr71.dll as a part of the binary
installer. That is ok, as those who has a license for Microsoft Visual
C++ 2003 is allowed to redistribute msvcr71.dll. Without a license for
Microsoft Visual C++ 2003 one it not allowed to redistribute this DLL.

This has some interesting implications:

** If you don't have Microsoft Visual C++ 2003, is it illegal to
redistribute the binary Python installer from Does
redistribution of Python also violate Microsoft's copyright on the CRT?
And if so, is someone developing in Python required to ask the customer
to download a binary installer from (instead of shipping
a copy)?

** Not everyone that develops in Python has a license for Microsoft
Visual C++ 2003. I have the Microsoft Visual C++ 2003 Toolkit, but it
only allows me to link and redistribute a static version of msvcr71.
So, does this prevent me from using Py2Exe?

** It is apparently not possible to buy a license for VS2003 anymore,
as the product has expired. One can only buy a new get a license for
VS2005, which allows redistribution of msvcr81.dll, but not
msvcr71.dll. Microsoft said something about a right to "downgrade the
compiler" once a license for VS2005 is bought, but I am not sure if
this applies to the crt redistribution rights as well.

I understand that Microsoft has donated Microsoft Visual C++ 2003
compilers to key Python developers. That is generous of them. But what
did they say about the crt licensing?

More information about the Python-list mailing list