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I've been pretty quiet about this, but over the last couple of months I have been trying to negotiate with Moxie a way to distribute the GPL licensed AxolotlKit

I've been pretty quiet about this, but over the last couple of months I have been trying to negotiate with Moxie a way to distribute the GPL licensed AxolotlKit on the iOS App Store in ChatSecure (which is open source). After being denied a license, I was told by Moxie that I would be unable to write a non-GPL AxolotlV3 implementation because there is not publicly available documentation, and that any re-implementation will necessarily be a derivative work because the source code must be consulted. You may notice the AxolotlV2 documentation has been removed... and there was never documentation for AxolotlV3. The only public spec is the original double ratchet, and a few blog posts, which don't include things like signed prekeys and 4-way DH.

moxie 10y ago
Hey Chris, as you know, we have no problem with you distributing our GPL software through the app store. Most of your communication has centered around asking us to change the license on our source base to something other than the GPL. We like the GPL for the quality control that it provides. If someone publicly says that they're using our software, we want to see if they've made any changes, and whether they're using it correctly. You don't like the GPL because you feel that it is incompatible with the Apple App Store, despite our feelings to the contrary. If you'd like to do the work of developing a strong copyleft version of the GPL that you feel is appropriate for use in the app store, and get it OSI approved, we'd certainly look at using that. As for documentation, there has never been a protocol called AxolotlV2. There was TextSecure, the crypto layer of which has evolved into Signal Protocol. We'd like to get this better documented so that people without crypto expertise can integrate it without having to talk to us, but that's a pretty heavy task that comes with a massive amount of responsibility, and some parts of this are still evolving. It's a priority, but we are taking the time to do it right, and hopefully we'll have more to publish this year. We haven't patented any of the concepts here, and we've done a lot to explain and popularize them. We're happy for people to use these concepts to build their own implementations of similar protocols, but we don't want people slapping things together and calling that Signal Protocol.
- deleted 10y ago
  [deleted]
- strcat 10y ago
  The FSF and SFLC take the position that the GPL is incompatible with the iOS App Store restrictions, since it forbids adding additional restrictions. However, GPL3 has official support for "additional permissions" and it's still FSF / OSI approved with those added. It permits dropping the additional permissions and using the software as pure GPL3. So that seems like the best approach, but Apple's restrictions are probably a moving target and it would erode the copyleft aspect of the license.
  - belorn 10y ago
    When the author say "we have no problem with you distributing our software through the app store", then I would just get that in some more official writing that include you, apple, and more detailed description on what permission is exactly given. The primary purpose of any software license is to shield the downstream distributor against being charged under copyright infringement, but a personal permission is equally fine in a legal sense so long you don't intend that downstream from you should also be able to distribute your version.
- nkobeissi 10y ago
  That's somewhat helpful but doesn't fully address Chris's story. Would Chris be able to write his own implementation, interoperable with AxolotlKit (the iOS Signal Protocol implementation), from scratch, without any explicit code reuse, and then publish it under whatever license he chooses? If the answer is yes, I strongly encourage you to publish an official statement from OWS stating so. I know for a fact that FOSS projects are losing their funding because of the impression that even if they write their interoperable implementation from scratch there would still be licensing questions. You've clarified this somewhat on Twitter before, but if you can publish a short statement on behalf of OWS, that would go a long way into clearing up the issue for a lot of free software developers. Thanks.
- mimi89999 10y ago
  It looks like you can publish GPL apps in the App Store if you are the author. If you want to use someone's GPL lib in your app, then you might have a problem...

moxie 10y ago

Hey Chris, as you know, we have no problem with you distributing our GPL software through the app store. Most of your communication has centered around asking us to change the license on our source base to something other than the GPL. We like the GPL for the quality control that it provides. If someone publicly says that they're using our software, we want to see if they've made any changes, and whether they're using it correctly. You don't like the GPL because you feel that it is incompatible with the Apple App Store, despite our feelings to the contrary. If you'd like to do the work of developing a strong copyleft version of the GPL that you feel is appropriate for use in the app store, and get it OSI approved, we'd certainly look at using that. As for documentation, there has never been a protocol called AxolotlV2. There was TextSecure, the crypto layer of which has evolved into Signal Protocol. We'd like to get this better documented so that people without crypto expertise can integrate it without having to talk to us, but that's a pretty heavy task that comes with a massive amount of responsibility, and some parts of this are still evolving. It's a priority, but we are taking the time to do it right, and hopefully we'll have more to publish this year. We haven't patented any of the concepts here, and we've done a lot to explain and popularize them. We're happy for people to use these concepts to build their own implementations of similar protocols, but we don't want people slapping things together and calling that Signal Protocol.

deleted 10y ago
[deleted]
strcat 10y ago
The FSF and SFLC take the position that the GPL is incompatible with the iOS App Store restrictions, since it forbids adding additional restrictions. However, GPL3 has official support for "additional permissions" and it's still FSF / OSI approved with those added. It permits dropping the additional permissions and using the software as pure GPL3. So that seems like the best approach, but Apple's restrictions are probably a moving target and it would erode the copyleft aspect of the license.
- belorn 10y ago
  When the author say "we have no problem with you distributing our software through the app store", then I would just get that in some more official writing that include you, apple, and more detailed description on what permission is exactly given. The primary purpose of any software license is to shield the downstream distributor against being charged under copyright infringement, but a personal permission is equally fine in a legal sense so long you don't intend that downstream from you should also be able to distribute your version.
nkobeissi 10y ago
That's somewhat helpful but doesn't fully address Chris's story. Would Chris be able to write his own implementation, interoperable with AxolotlKit (the iOS Signal Protocol implementation), from scratch, without any explicit code reuse, and then publish it under whatever license he chooses? If the answer is yes, I strongly encourage you to publish an official statement from OWS stating so. I know for a fact that FOSS projects are losing their funding because of the impression that even if they write their interoperable implementation from scratch there would still be licensing questions. You've clarified this somewhat on Twitter before, but if you can publish a short statement on behalf of OWS, that would go a long way into clearing up the issue for a lot of free software developers. Thanks.
mimi89999 10y ago
It looks like you can publish GPL apps in the App Store if you are the author. If you want to use someone's GPL lib in your app, then you might have a problem...