The kde-plasma-yawp software itself is GPLv2+, but concerns were raised around the terms of service about the data it uses. kde-plasma-yawp includes a dataengine that provides data from accuweather, whose terms of service is here: http://www.accuweather.com/termsofusage.asp?partner=accuweather&traveler=0
We're not bundling any of their content, are we? If so, I don't think this is an issue, otherwise, Firefox wouldn't be acceptable. :) Lifting FE-Legal.
Thanks.