See https://developer.mozilla.org/en-US/docs/NSS/NSS_3.14_release_notes . Release notes for NSPR seem harder to find, but you can look at the LICENSE file inside the tarball. Please update LICENSE= field in the ebuilds.
+ 16 Jan 2013; Lars Wendler <polynomial-c@gentoo.org> nss-3.14.ebuild, + nss-3.14.1.ebuild: + Converted MPL-1.1 to MPL-2.0 license (bug #452588). + + 16 Jan 2013; Lars Wendler <polynomial-c@gentoo.org> nspr-4.9.1.ebuild, + nspr-4.9.2.ebuild, nspr-4.9.2-r1.ebuild, nspr-4.9.4.ebuild: + Converted MPL-1.1 to MPL-2.0 license (bug #452588). +