I installed using tarball.In the wiki page everything went fine before the Configuration with WAF started.I am able to run WAF commands by prefixing "python" and not without it.
vaibhav@ubuntu:/media/New Volume/tarballs/ns-allinone-3.14.1/ns-3.14.1$ dir
AUTHORS CHANGES.html LICENSE RELEASE_NOTES test.py utils.py waf waf.bat wutils.py
bindings doc ns3 scratch testpy.supp utils.pyc waf-1.7.0 waf-tools wutils.pyc
build examples README src utils VERSION waf-1.7.0.tar.bz2 wscript
vaibhav@ubuntu:/media/New Volume/tarballs/ns-allinone-3.14.1/ns-3.14.1$ python test.py
/bin/sh: 1: ./waf: Permission denied
Waf died. Not running tests
vaibhav@ubuntu:/media/New Volume/tarballs/ns-allinone-3.14.1/ns-3.14.1$