There are times I love the Nerd Vittles site – they come up with some interesting and clever ways to use the Asterisk PBX. And then again, every so often, there are times when I actually read their instructions and wonder, “Why are they doing it that way?” It just seems like they are either making things a bit more difficult than they need to be, and/or doing things in a non-standard way that could cause problems down the road when the underlying software is updated. As an example, many Asterisk “all in one” distributions (including PBX in a Flash, the package promoted on the Nerd Vittles site) use both Asterisk and FreePBX as their underlying software. FreePBX in particular has a nasty habit of “breaking” existing installations if you upgrade the FreePBX software and are running anything outside their GUI — even third-party FreePBX modules aren’t safe (if you’re into this stuff, you might have read about the recent brouhaha with the Custom Contexts module — I don’t want to get into that issue in this article, but suffice it to say that if I spoke my mind on the subject, the FreePBX developers probably wouldn’t like me very much). So, when I read the article Tweaking Asterisk for Free Google Voice Calling on the Nerd Vittles site, I thought it was a great idea, but just didn’t care for the way they implemented it.

See more here:
How to use Google Voice for free outgoing calls on an Asterisk/FreePBX system (the easy way)