[asterisk-users] FXO Cards - T38

[Tzafrir Cohen]

On Sun, Feb 24, 2008 at 04:35:35PM +1100, Rob Hillis wrote:
> Your original comment was that you cannot use T.38 and G.729 in Asterisk
> at the same time.  On a technical level, this is /not/ true, especially
> if the T.38 implementation does not rely on SpanDSP. (whether or not
> such an implementation exists is another question)  Breaking license
> conditions is a separate issue altogether.

That is correct. The incompatibility is not inherent to the T.38
interface in Asterisk. Rather, to its implementation using SpanDSP code
in app_fax.

> I'm also curious as to why you assert that using G.729 in Asterisk
> (/not/ ABE) at the same time as a T.38 implementation that relies on
> SpanDSP since these are two completely separate plugins that are
> installed and acquired separately.  

They are not installed separately. They are modules loaded into the same
memory space. 

> That's almost like asserting that
> you can't run any commercial X application if you've installed my XYZ
> web browser on the same machine.   Just because they use a common
> software base (X in this instance) /doesn't/ mean that you're violating
> the GPL by running non commercial software on the same machine.

Those are two separate processes. Completely separate from one another.
This is a common misunderstanding of the GPL (or of the application of
copyrights laws to computer software).

> 
> A more meaningful interpretation of the GPL would be that you either can
> or can't run a T.38 implementation with Asterisk /full stop/.  Either
> the license is compatible, or it isn't.  Trying to force any other
> interpretation on people will end up with you being dismissed as an
> extremist.

Here is where things get interesting:

If we set aside proprietary licenses such as the ABE, we will see that
Asterisk is, in fact, dual-licensed.

1. GPL
2. GPL + exception

(2) is the LICENSE file in the Asterisk source tree. (1) is what has
enabled so far linking with [rt]x_fax, app_fax and linking with mysql
(at least in the past it was necessary for mysql. Not exactly sure now).

But if you use (1) non of the exceptions apply. And specifically, you
cannot link it with code whose usage is even limited such as the g729 codec.

-- 
               Tzafrir Cohen
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