The Federal Communications Commission is trying to convince people that it isn't banning third-party router firmware such as DD-WRT despite issuing guidance that sounded an awful lot like a ban.

Back in March, the FCC issued a Software Security Requirements document that said manufacturers applying for equipment authorizations should "Describe in detail how the device is protected from 'flashing' and the installation of third-party firmware such as DD-WRT." Applicants also had to answer the question, "What prevents third parties from loading non-US versions of the software/firmware on the device?"

Upon receiving criticism, the FCC insisted that there was no ban on software like DD-WRT and OpenWRT, saying instead manufacturers must prevent devices from working outside their allowed frequencies, types of modulation, and power levels so as not to interfere with other systems.

But that guidance still remained on the books, and the easiest way to comply was likely to disable installation of third-party firmware by users altogether. Today, the FCC issued an updated version of the guidance that strips out the DD-WRT reference. Instead, it now says:

Describe, if the device permits third-party software or firmware installation, what mechanisms are provided by the manufacturer to permit integration of such functions while ensuring that the RF parameters of the device cannot be operated outside its authorization for operation in the US. In the description include what controls and/or agreements are in place with providers of third-party functionality to ensure the devices’ underlying RF parameters are unchanged and how the manufacturer verifies the functionality.

FCC Engineering and Technology Chief Julius Knapp also wrote a blog post titled, "Clearing the Air on Wi-Fi Software Updates." The previous guidance raised the question of whether the FCC was "mandating wholesale blocking of Open Source firmware modifications," Knapp wrote.

"We were not, but we agree that the guidance we provide to manufacturers must be crystal-clear to avoid confusion," he wrote. "So, today we released a revision to that guidance to clarify that our instructions were narrowly focused on modifications that would take a device out of compliance."

It's still possible for manufacturers to comply by preventing loading of any third-party firmware, but the new language could reduce the likelihood of that happening.

Separately, the FCC in July proposed a new requirement for device manufacturers to “implement well-defined measures to ensure that certified equipment is not capable of operating with RF-controlling software for which it has not been approved.”

This also drew criticism during a public comment period that expired this week. The issue "generated thousands of comments from individuals concerned that the proposal would encourage manufacturers to prevent modifications or updates to the software used in devices such as wireless local area networks (e.g., Wi-Fi routers)," Knapp wrote. "Eliciting this kind of feedback is the very reason that we sought comment in an NPRM [notice of proposed rulemaking] and we are pleased to have received the feedback that will inform our decision-making on this matter."

The FCC still has to finalize rules, and Knapp said the commission "welcome[s] continued input from manufacturers, users, technologists, and others."