Halo 2 BOSL Impact on Zcash Forks

heyrhett · April 29, 2022, 11:54pm

Zcashd is MIT licensed,
Zcashd includes Halo 2, which is BOSL licensed

Are forks of the zcashd repository allowed?
If not, would they be allowed if the Halo 2 code was removed and replaced with a pointer to it?

Thank you, I’m not a lawyer and want to follow the licenses properly. Not familiar with BOSL libraries

Shawn · April 30, 2022, 12:56am

https://github.com/zcash/halo2/blob/main/LICENSE-BOSL

https://notes.andymatuschak.org/z2B4XzXo1mDV3ydhWanGxDMYWKXCQfX6mCiS

heyrhett · April 30, 2022, 1:02am

github.com

zcash/zcash/blob/master/COPYING

Copyright (c) 2016-2022 The Zcash developers
Copyright (c) 2009-2022 The Bitcoin Core developers
Copyright (c) 2009-2022 Bitcoin Developers

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN

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Shawn · April 30, 2022, 1:05am

heyrhett · April 30, 2022, 1:09am

Hi, so my interpretation is that since the zcashd code is MIT license, it can be forked because “MIT is a permissive license”

Is that correct or no?

Shawn · April 30, 2022, 1:22am

Disclaimer: I am not familiar enough with the BOSL or the MIT license to comment with any authority.

However, my limited understanding of the subject, is that Halo2, and the Zcash Orchard payment protocol (which is what you would be forking) are under two separate licenses.

To foster greater collaboration and reuse, Halo 2 is now shared under the more common and permissive MIT license or Apache 2.0 license. Orchard, the Zcash payment protocol built on Halo 2, will remain under BOSL.

So, I believe that means the ECC crate, which has the Orchard circuit, is still under BOSL.

Thereby, if you fork Orchard it would fall under BOSL, not MIT.

CC @str4d if I am correct?

str4d · April 30, 2022, 1:34am

(I am not a copyright lawyer, or any kind of lawyer for that matter.)

@Shawn is correct. The relevant copyright info is here, showing the exception that enables the zcashd and zebrad codebases to be generally licensed as MIT instead of BOSL:

github.com

zcash/zcash/blob/d6db09a180d57b60889131a1ad3dac1d96afe828/contrib/debian/copyright#L163-L166


      
          Files: depends/*/vendored-sources/halo2/*
           depends/*/vendored-sources/orchard/*
          Copyright: 2020-2022 The Electric Coin Company
          License: BOSL-1+ with Zcash exception

github.com

zcash/zcash/blob/d6db09a180d57b60889131a1ad3dac1d96afe828/contrib/debian/copyright#L1672-L1705


      
          License: BOSL-1+ with Zcash exception
           This package ("Original Work") is licensed under the terms of the Bootstrap Open
           Source License, version 1.0, or at your option, any later version ("BOSL"). See
           the file ./LICENSE-BOSL for the terms of the Bootstrap Open Source Licence,
           version 1.0.
           .
           Only if this Original Work is included as part of the distribution of one of the
           following projects ("the Project"):
           .
           - The Zcash projects published by the Electric Coin Company,
           - The Zebra project published by the Zcash Foundation,
           .
           then License is granted to use this package under the BOSL as modified by the
           following clarification and special exception. This exception applies only to
           the Original Work when linked or combined with the Project and not to the
           Original Work when linked, combined, or included in or with any other software
           or project or on a standalone basis.
           .
               Under the terms of the BOSL, linking or combining this Original Work with
               the Project creates a Derivative Work based upon the Original Work and the

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Forking zcash/zcash would result in a distribution that falls outside the exception, and therefore would require either:

Distributing the fork per the BOSL terms, which (AIUI - I am not your lawyer) would allow the fork to continue being licensed as MIT for up to a year, but would then require relicensing as BOSL after that point.
Obtaining a similar exception from ECC, to allow the fork to be distributed under the MIT license beyond a year (per whatever terms the exception might have).
Removing the BOSL-licensed code from the fork, namely the orchard crate (and also the halo2* crates if the fork was made now, but zcashd 5.0.0 will use the MIT-licensed halo2* crates instead of the earlier BOSL-licensed versions).

heyrhett · April 30, 2022, 8:10am

Thank you for the clear explanation.

Zzzzzz · May 1, 2022, 6:17am

FYI - the Zclassic account(I assume run by Rhett) has been tweeting this and other similar tweets