Active-Ergative langs (was Re: Ke'kh - degrees of volition)

Daniel wrote:
> Teoh wrote:
>
>> Which natlangs are active? Are there any references on the Net on those?
>> I'd like to see a "real", active natlang in action :-)
>
> Well, the ones I've looked at are Guaraní from SAmerica; The Caucasian
> langs Georgian and Ts'ova-Tush; Lakhota, Mohawk, Chickasaw and Eastern
> and Central Pomo from North America and the Austronesian lang Acehnese.
>
I was wondering if there is a difference between the terms ergative and
active.  I thought that ergative referred to the following pattern:
E    ist  a    Jan   0  tiek.
PERF open ERG  John  ABS  door.
'John opened the door.'

E     ist     0     tiek.
PERF  open    ABS   door.
'The door opened.'
(Example from my own Skerre)

whereas active was a subset of ergative where the semantics of the sentence
made a difference as to whether the ergative showed up or not.
Le         betõ   nelo     kebõ.
The.ERG    boy    PAST.he  fall
'The boy fell' (and he meant to do it)

Li        betõ   nelo    kebõ.
The.NOM   boy    PAST.he fall.
'The boy fell' (on accident)

(These examples are devised by me, but from Teonaht, invented by Sally
Caves, so no guarantees that they are 100% grammatically right).

So that would make all active languages ergative, but not all ergative
languages active. But I've heard ergative and active used interchangeably.
What exactly is going on here?

-Doug