[pmorici]

Sparkfun has a reasonable run down of FCC rules.

https://www.sparkfun.com/tutorials/398

In this guys case there is an FCC allowance that you can build up to five devices for personal use that this cellphone project might fall under. Building a bunch to sell is a different matter though, especially since this is an intentional radiator vs. a unintentional one.

I get the sense that it's a bit of a taboo topic to talk about publicly in the opensource / hobbyist world. Adafruit and Sparkfun, the two major outlets for hobby electronics in the USA, for example generally won't discuss publicly what the companies stance on their FCC rules compliance obligation is.

My feeling based on reading a bit about it is that until you reach a certain scale the cost of FCC testing is prohibitive. So when companies like Sparkfun and Adafruit were starting out they simply followed best design practices and fudged a little on the FCC side of things by saying that their products fell under one of the exceptions or that they use a pre-certified module. Now that they are bigger it seems a small number of their products actually do get certified. It's a mess for sure.