This article is old but interesting. I've this router and I've Verizon's FIOS service. Not long after purchasing this service, I perused Actiontec's website and had seen that they utilized Linux (this is, specifically, an issue with Verizon not including the source code for BusyBox to its customers, per v2 of the GPL) as the firmware for this router. I also saw that Verizon offered firmware versions for this router on their pages. I didn't think that they'd not release their software as GPL, though. I think it was either forgotten or GPL was taken for granted (because GPL software is usually free).
Anyways, this is a good read.