The license agreement is (copied and pasted from the download page):
Copyright 1996 by A K Peters, Ltd.
Reproduction of the downloaded version is permitted for any valid
educational purpose of an institution of learning, in which case only
the reasonable costs of reproduction may be charged. Reproduction for
profit or for any commercial purposes is strictly prohibited.
If you're still having trouble accessing it, here are direct links to the mirrors:
http://www.math.upenn.edu/~wilf/AeqB.pdf
http://www.math.rutgers.edu/~zeilberg/AeqB.pdf
http://www.fmf.uni-lj.si/aeqb/AeqB.pdf
The license agreement is (copied and pasted from the download page):