Miredo is an implementation of the Teredo – IPv6 over IPv4 tunnelling protocol which I have been playing with lately. I have filed an ITP bug to get Miredo into Debian, however this has been delayed while I try and get a handle on some of the patent issues surrounding the Teredo protocol. While Miredo itself is licensed under the GPLv2 the state of the Toredo protocol is less clear.

Teredo was created by Christian Huitema, an architect with Microsoft. It is currently a Proposed Internet Standard waiting for the IETF editor to review it and assign an RFC number for it, IANA will then assign a permanent prefix for use by Teredo clients, servers and relays.

According to the IETF IPR disclosure page, Microsoft has filed a statement of claim against the technologies described in the Proposed Standard. Microsoft states that they will provide a Royalty-Free, Reasonable and Non-Discriminatory License to All Implementers in their statement. Specifically the license that they offer the Teredo protocol under is called the Microsoft Royalty Free Protocol License Agreement. This is a catch-all license that Microsoft uses for all client-server protocols used by Windows. The license itself doesn’t make any claims about Microsoft’s IP rights, it simply gives you a license to use any rights Microsoft may have in the specific protocol you are using. For example at the end of the license agreement you select which protocols you wish to have covered under the agreement. Alongside Teredo you can also choose protocols such as IPv4, DNS, 6to4 and lots of other common protocols.

The actual patent application for Teredo is incredibly difficult to find, the IETF IPR disclosoure doesn’t link to it, none of the proposed standards link to it and googling for “Teredo Patent Application” isn’t particularly successful either. In the end it turns out that the title is quirkily named “Allowing IPv4 clients to communicate over an IPv6 network when behind a network address translator with reduced server workload” and was published as Patent Application 20040190549 on the 30th September 2004.

• USPTO Patent Application 20040190549
• PDF Download of full original application (with diagrams) from the EU patent office – Click the ‘orginal document’ tab, cancel the download window that pops up (unless you only want the 1st page), then select ’save full document’ from the title bar above the tabs and go through the captcha form.

Incidentally if anyone knows of a nicer way to link to a US Patent Application than the ugly URL above, I would love to know.

Half the reason that the Patent Application was hard to find is that it doesn’t actually mention Microsoft anywhere at all, unlike the ~5000 odd other Patent Applications currently filed by Microsoft. From what I can tell it appears that Christian Huitema has filed the application through is own personal attorneys independently of Microsoft.

So where does this leave us in terms of getting Miredo into Debian? The short answer is I’m not entirely sure.

I can’t seem to find a definitive statement regarding Debian’s position on patents anywhere, the best I’ve been able to come up with is a debian-legal post from Andrew Suffield from Jan 2005 which offhandedly describes the informal Debian patent policy as:

“ignore patents until somebody starts to wave them around, then drop the offending thing like a hot rock”

So maybe I’ve already shot Miredo in the foot, by investigating its Patent Status…

My take on the situation seems to be that Debian is perfectly happy (and perhaps has no other option but) to ignore patents applicable to software in Debian until it becomes apparent that a particular patent is being enforced or has the potential to be enforced.

So the question now becomes whether the Microsoft Royalty Free Patent License is acceptable enough to Debian to allow Miredo to be included in main or non-free, or whether it simply can’t be redistributed at all. The main problem I see with the license is that it does not permit you to sublicense other parties to make use of the Toredo technology used by Miredo. If this were a copyright license then that would most certainly fail to pass the Debian Free Software Guidelines, does Debian treat patents in the same manner?

I think it’s time for me to post to debian-legal to seek some “official” guidance on the situation, but hopefully this post has ordered my thoughts enough that I can now write a coherent mail seeking help. If you have any comments or pointers to Debian statements on this sort of situation that I have missed they would be most welcome.