The errata just rehashes the existing wording with no change in effect.

This means that Gladius of Light still does half damage as listed.

(Or you've forgotten the Errata for Gladius of Light itself).

could you unwrap that a bit more?

Ummm Gladius of Light specifically states it effects Undead, Spirits, and Infernals....

One point, with this rule in effect a couple of battles in the delve at ArcanisCon would have been impossible for some tables - especially newbies

which is why its Encounter Value will be going up significantly

But

just start looking for spells which target undead or grant/create/make a.. weapon magical.

Sounds like an 'arms race', but using spells instead of collecting gear. "Sorry Bob, we can't take you on the delve, you don't have spells that'll target undead or grant/create/make a weapon magical"

As discussed a few weeks ago, that wording fails Gladius of Light, as it targets Undead and not Incorporeal creatures.

With the new errata, runes, spells, effects, etc, must specifically say Incorporeal to effect an Incorporeal creature. Gladius of light saying effecting Undead doesn't mean it ignores the 1/2 damage if the Undead is Incorporeal.

Solid point which will be covered in errata..

see under gladus of light & benediction of the gods