The file base64.h distributed with xmlrpc++ seems to be an unlicensed file. It appears to originate from an article at code guru [1], where it does not include any license information.

The file itself contains an email address that is no longer valid. I got an instant bounce when attempting to send an email to it. I also raised an issue at the xmlrpc++ sourceforge page [2], and I contacted code guru for their view on the matter (although I don't believe their view matters).

Without a license we can't technically redistribute the file. So unless we can find a license for the file it seems it needs to be replaced with a different base64 implementation.

See also [3] for a related discussion on discourse.

[1] http://www.codeguru.com/cpp/cpp/cpp_mfc/article.php/c4095/STL-Compatible-Base64-Encoder.htm
[2] https://sourceforge.net/p/xmlrpcpp/discussion/240494/thread/cec40381/
[3] https://discourse.ros.org/t/ros-gnu-gpl-v1-2-issue/1642/4