Licensing a-la-carte. Also, libGL.la is gone.

Apparently Gentoo recently enabled a per-package license approval feature for portage.  As with most things Gentoo, the feature was discovered unceremoniously when I tried to do 'emerge -uDavt world' and it complained loudly in new and confusing ways.  But a quick investigation shed light on the issue, and I set about making the small changes necessary to become compliant.

Basically, Gentoo now maintains a (comprehensive) list of licenses with which any given portage package might be associated.  And portage treats the licenses as opt-in, meaning that it doesn't presume that you're willing to accept them.  Also, just like use flags, there is an emerge variable (ACCEPT_LICENSE) that can be set for all packages in make.conf.  It defaults to '* -@EULA', which means all licenses are accepted automatically except any within the 'EULA' group.  A full list of licenses and groups is available in /usr/portage/profiles/license_groups.  Overrides to this variable can be made on a per-package basis using a dedicated file: /etc/portage/package.license.

I elected to leave ACCEPT_LICENSE at its default, and use the package.license file to individually manage non-free licenses.  Thus I needed to create a package.license file with the following contents:

dev-java/sun-jdk dlj-1.1
app-emulation/virtualbox-ose-additions PUEL
net-im/skype skype-eula

Obviously, those were only necessary because I have (or want to have) those packages installed.  Your package.license file might contain completely different entries.  With those exceptions in place, emerge went on its merry way and so did I.  Note that this process doesn't alleviate the need to say 'yes' to certain package licensing verbage at emerge-time. 

Unrelatedly, as of 20100131, the gentoo overlords have removed libGL.la, saying thus:

Eselect-opengl package now strips the libGL.la file. This file was broken and
thus we proceeded with its removal. It brings slight inconvenience on you fellow
users. After emerging the new version =app-admin/eselect-opengl-1.1.1-r2 please
emerge one more package dev-util/lafilefixer and use it for fixing all various
compilation issues by running as root:
# lafilefixer --justfixit
Note that not-running this command will bring you compilation issues so you
should really pay attention to this message and act upon it.

Oh, act upon it I did.  By taking precisely the suggested actions.