[collectd] New to collectd - About licence of plugins

[Florian Forster]

Hello Arthur,

I am not a lawyer, just so you know.

On Tue, Apr 04, 2017 at 10:18:23PM +0200, Arthur Havlicek wrote:
> I intend to build a business around this amazing tool, mostly
> selling a collectd integration + plugins. AFAIK plugins in collectd
> are compiled with the daemon making it a single binary, as such it
> can be considered derivative work under a GPL licence.

There are three points to this:

1) The daemon is licensed under the MIT license, not the GPL. [*]

2) The daemon and plugins are not compiled into a single binary. The
   daemon is an executable binary and each plugin is compiled into a
   shared object. However, the plugins dynamically link with / import
   symbols from the daemon.

3) Whether dynamically linking creates a derived work is a matter of
   debate (e.g.: http://www.linuxjournal.com/article/6366).

   The argument of the FSF is that by linking the plugin with the daemon
   you're coping parts of the daemon into the plugin, creating a derived
   work. Hence, they argue, even if you link dynamically against GPL'ed
   code, the resulting binary contains GPL'ed code and needs to be
   considered to be licensed under the GPL.
   
   Personally, I strongly disagree with this interpretation: I think
   that by linking (dynamically!) you're using an interface in the way
   it was intended to be used and not creating a derived work.
   
   To make matters worse, some think that when the licensing terms are
   ambiguous, the *intend* of the author(s) becomes relevant, which is
   of course very hard to detemine in an open source project with many
   contributors.

   Luckily, due to 1), none of this really applies to your plans.

> I wanted to know whether a non-free licencing over a collectd plugin
> was considered respectful of collectd licence in itself. I expect this
> to be the original wish of collectd to enable as much contributor as
> possible and allow they licence their work the way they want, but I
> found no other example yet or documentation that this is even possible
> to release a modified collectd package containing non-free plugins
> which is restricted.

Personally I'd prefer if you would share your work with the general
public, but the MIT license is not a copyleft license, i.e. you're free
do distribute a binary of the daemon with proprietary plugins without
having to disclose your sources.

Best regards,
—octo

[*] While writing this I discovered that the daemon links in
    "src/daemon/utils_ignorelist.c", which is GPL'ed, but isn't using it
    itself. I'll shortly change this so the plugins using the
    "ignorelist" utility link against it themselves, so that the daemon
    binary is purely MIT licensed.
-- 
collectd – The system statistics collection daemon
Website: http://collectd.org
Google+: http://collectd.org/+
GitHub:  https://github.com/collectd
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