sys-devel/llvm-2.4 in java-overlay has LICENSE="LLVM", but that license does not exist. A license file must be added to java-overlay/licenses/ or the LICENSE setting changed in java-overlay/sys-devel/llvm/llvm-2.4.ebuild (or both). Side note: the main portage tree now has licenses/UoI-NCSA. This may be the right license for the LICENSE variable; it is a template which does not exactly match <URL:http://llvm.org/releases/2.6/LICENSE.TXT> so perhaps further action may be necessary here.
And llvm 2.6 is in the main tree now
llvm is in main tree now