> (try getting help with DAHDI if you aren't using it).
I mean, is it shocking that the Digium Asterisk Hardware Device Interface is primarily supported with Asterisk?
> I'm just curious if it's and product worth learning how to hack on.
Asterisk, Freeswitch, and Kamailio are the main open source telephony projects and are all also widely used as the "open core" of proprietary solutions so yeah there's plenty of room to make money selling support or addons for these projects.
That said, as someone who has been supporting Asterisk and Freeswitch for years now, I can't say I've ever had a situation where a DAHDI interface made sense over just using a standalone PSTN<>SIP gateway. Letting an Adtran TA9xx take care of integration with the PSTN and having the PBX side be pure VoIP makes things so much easier and more flexible IMO. The PSTN line is just one more SIP trunk, and any analog extensions we may have hooked up to FXS ports are just SIP extensions as far as the server is concerned.
If you want to dip your toes in I'd recommend setting up a FreePBX (Asterisk) or FusionPBX (FreeSwitch) instance. That gets you a nice web interface that you can point and click your way through to a usable setup while still being able to poke around at a low level as you learn how the system works.