Re: [boost] BOOST license & GPL

Subject: Re: [boost] BOOST license & GPL
From: Andrey Semashev (andrey.semashev_at_[hidden])
Date: 2017-04-01 10:58:45

On 04/01/17 07:20, Oliver Kowalke via Boost wrote:
> Hi,
>
> I encountered a open source project that is released under GPL and uses
> Boost - that's OK, because GPL and Boost license should be compatible.
>
> But the developers of those project copied code from Boost into their own
> library.
> The question is, is this new library now GPL or Boost license?

[Standard disclaimer that I'm not a lawyer, and the following is my 
understanding.]

Boost license (BSL) requires to "be included in all copies of the 
Software, in whole or in part, and all derivative works of the Software, 
unless such copies or derivative works are solely in the form of 
machine-executable object code generated by a source language 
processor." So the copied part is still under the Boost license (and the 
license must be present in that project in a way that makes it clear 
what code it applies to). However, the developers of that project can 
distribute their project as a whole under the GPL, including the parts 
under the BSL. They cannot distribute the BSL parts alone under another 
license, such as GPL.

Here are some related info:

Explains about including public domain code into a GPL-ed program; I 
don't see why the same wouldn't apply to BSL-ed code:

https://www.gnu.org/licenses/gpl-faq.en.html#CombinePublicDomainWithGPL

Describes combining a module with a GPL-ed program:

https://www.gnu.org/licenses/gpl-faq.en.html#GPLModuleLicense

Describes how GPL applies to combined work:

https://www.gnu.org/licenses/gpl-faq.en.html#GPLIncompatibleAlone

> Additionally, because they copied the code from several Boost files into
> one, they mixed up copyright statements. As a result, some people get
> copyright on code they never wrote.

Yes, the copyright list is confusing, IMHO. As I understand it, the list 
of copyright holders shows the parties that have written/modified 
substantal *parts* of the source file. This follows from the normal use 
of this list: when you modify a lot of content in a file, you typically 
*add* yourself to the existing list of copyright holders; you don't have 
to rewrite the file from scratch for that.

The point is that, for example, in case of changing the license on the 
code all copyright holders in the list have to be contacted for 
approval, even though each copyright holder alone did not write the 
whole file. Each copyright holder can give the permission on the part he 
wrote. Determining who wrote which part can be difficult, so "all or 
none" approach is quite possible in such cases.