Re: [PATCH 04/10] meson: option to build as shared library

[Daniel P . Berrangé]

On Tue, Oct 13, 2020 at 04:41:06PM +0200, BALATON Zoltan wrote:
> On Tue, 13 Oct 2020, Daniel P. Berrangé wrote:
> > On Mon, Oct 12, 2020 at 04:29:33PM -0700, Joelle van Dyne wrote:
> > > From: osy <osy86@users.noreply.github.com>
> > > 
> > > On iOS, we cannot fork() new processes, so the best way to load QEMU into 
> > > an
> > > app is through a shared library. We add a new configure option
> > > `--enable-shared-lib` that will build the bulk of QEMU into a shared lib.
> > > The usual executables will then link to the library.
> > 
> > Note that QEMU as a combined work is licensed GPLv2-only, so if an app is
> > linking to it as a shared library, the application's license has to be
> > GPLv2 compatible. I fear that shipping as a shared library is an easy way
> > for apps to get into a license violating situation without realizing.
> 
> Please don't let that be an obstacle in merging this series. They'll do it
> anyway as seen here so having it upstream is probably better than having a
> lot of different/divergent forks.

"They'll violate the license anyway" is not a compelling argument.

> In case of UTM it seems to be licensed under Apache License 2.0:
> 
> https://github.com/utmapp/UTM/blob/master/LICENSE
> 
> which FSF says not compatible with GPLv2 but it is with GPLv3:
> 
> http://www.gnu.org/licenses/license-list.html#apache2
> 
> Not sure however if that's for using Apache licenced part in GPLv2 code or
> the other way around like in UTM in which case I think the whole work will
> effectively become GPLv3 as most parts of QEMU is probably GPLv2+ already or
> BSD like free that should be possible to combine with only files explicitely
> GPLv2 in QEMU remaining at that license and UTM parts are Apache 2.0 when
> separated from QEMU. I have no idea about legal stuff whatsoever but
> combining two free software components should be legal some way (otherwise
> it's not possible to combine GPLv2 with GPLv3 either).

You need to distinguish between GPLv2-only and GPLv2-or-later.

GPLv2-or-later is fine as that upgrades to GPLv3 when used in a
combined work with Apache License or GPLv3 software.

GPLv2-only will, by design, *not* upgrade to newer GPL versions
when combined - it is simply license incompatible.

QEMU unfortunately has a bunch a GPLv2-only code present that we
cannot eliminate.

Regards,
Daniel
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