LGPL a possibility for Breeze Qt widget style?

[Elvis Stansvik]

Hi Plasma folks!

This is probably a long shot, but here it goes.

At work we're currently building a desktop application for viewing the
results coming out of the analysis machine we're developing. The
application is to be deployed to select customer workstations, which
will all be running Kubuntu 16.04 + Plasma.

So far we've tested this internally by packaging the application as a
regular Ubuntu package and delivering it to the workstations through
our own (to be customer-facing) APT repo. We're using the
system-provided Qt (under the LGPL), and our application, being a Qt
application, fits in nicely thanks to Qt picking up the Breeze Qt
widget style.

I'm now exploring the option of packaging the application as an
AppImage instead (or maybe one of the alternatives that have become
popular recently), which would give us greater freedom in picking the
Qt version to use (and versions of other libraries).

One thing that is a bit of a stumble block with this is that the Qt we
would bundle in such an AppImage will not pick up the system-installed
Breeze Qt style, making our app look out of place on the Plasma
desktop among other Qt and KF5 apps.

A solution would be to bundle a version of Breeze inside the AppImage,
linked against the Qt version we're bundling. But this led me to the
discovery that Breeze is under GPL, which I believe would prevent us
from doing so (our app is closed source for now, a decision beyond my
control). I was sort of expecting LGPL, like KF5.

Has anyone else been in the same boat? Has the licensing of the Breeze
Qt widget style been discussed before? Would it be
possible/feasible/acceptable to also offer it under LGPL for use cases
like this, when a closed source app wants to look native, but wants to
bundle its dependencies?

Thanks in advance,
Elvis