This is the Copyright of the MNIST dataset:

Yann LeCun (Courant Institute, NYU) and Corinna Cortes (Google Labs, New York) 
hold the copyright of MNIST dataset, which is a derivative work from original 
NIST datasets. MNIST dataset is made available under the terms of the 
Creative Commons Attribution-Share Alike 3.0 license.

More information can be found here:
http://www.pymvpa.org/datadb/mnist.html