Just came across Johanne Torres' interesting article: DVG-1402S: The First Unlocked VoIP Router?
In the suit, SIPphone demanded that Vonage properly label boxes and advertisements to list the mandatory fees and restrictions of their locked hardware, which I wrote about awhile back in this blog entry. I'm all for open standards, so I tended to side with SIPPhone from a moral standing, but that doesn't mean that Linksys and Vonage were doing anything illegal. Partnering is as much a part of capitalism as anything else.
Anyway, it appears that in her article, Johanne Torres mentions the D-Link DVG-1402S is now supported by SIPPhone, and the article also states that the D-Link DVG-1402S is the first "ATA firewall/router combo" from a major manufacturer - namely D-Link that is not tied to a specific VoIP service provider. (Most router/firewall ATA devices are locked to a specific VoIP service provider.)
I should mention that Zoom also has an "unlocked ATA" which I recently reviewed, but unlike most ATAs, their ATA is not only a firewall/router ATA device but it features an integrated DSL modem - but it does require DSL service to work - cable broadband users need not apply! Actually, I take that back. I just recalled that 2 out of the 3 Zoom products are DSL-based, but they do offer an "unlocked SIP-based ATA router/firewall combo" - the Zoomtel V3 Model 5567 that works with cable broadband, DSL (using your existing DSL modem), or other IP connectivity.
So I guess technically there are two manufacturers offering unlocked ATAs, but Zoom is certainly less well-known than D-Link, so maybe they don't fall under the "major manufacturer" category stated in Johanne's article.
The D-link DVG-1402S hasn't been out long, but it already has started to build a fan-base. For instance, there's an interesting 2-page thread in the VoIP Forum about the D-Link DVG-1402S titled "Need To Unlock D-Link DVG-1402S" you should go check out.
Updated: Hmmm, it appears Linksys was also offering an unlocked ATA but pulled it from the market.
Did I miss any others? Let me know...