This probably isn't a priority for anyone but, I'd like to propose that
the license tag have a version attribute
http://www.ros.org/wiki/Manifest/XML#A.3Clicense.3E_tag

<license url="http://www.gnu.org/licenses/lgpl.html"
version="3.0">LGPL</<license>

It may also be worth including in a REP somewhere examples of common
values so we don't end up with every possible permutation of "lesser
GPL", "lgpl", "LGPL", "LGPLv3", etc.