[erlang-questions] A PropEr announcement

Richard Carlsson <>
Tue Jun 14 21:28:26 CEST 2011

On 2011-06-14 19:50, Daniel Luna wrote:
> The GNU GPL has always allowed for linking with "system libraries" and
> in version 3 that now explicitly includes the standard libraries of
> common programming libraries.
 > So I don't know whether older versions of GPL are incompatible with
 > Erlang or not, but it seems clear cut that version 3 is.

GPL v2 talks rather specifically about only "the major components 
(compiler, kernel, and so on) of the operating system on which the 
executable runs", which does not seem to cover things like runtime 
libraries of a language implementation apart from the language the OS is 
written in. You're right that v3 seems to be much more "modern" in this 
regard, so the libraries and runtime system of the Erlang/OTP standard 
distribution are probably not a problem under GPL v3.

Still, any other software (i.e., your tests) specifically designed to 
depend on PropEr as currently published under the GPL would itself have 
to be offered under the terms of the GPL.

> Generally I would not recommend LGPL, but would rather recommend that
> Kostis dual licenses the software. Most (if not all) users would be
> fine with GPL. The few that really, really want to give the tests to
> their clients without also giving away the source code, could then
> purchase a closed source version of the software.

There are many open source projects that wish to include their test code 
as part of their distribution, both because it's easier not to strip 
them out, and because their users may want to run the tests. If they 
want to distribute their main code offering under a non-copyleft license 
like MIT or Apache - it's their choice - they could only do that by 
splitting the code into one non-copyleft distribution without the tests 
and one GPL-compatible distribution with the tests. That's asking quite 
a lot of your poor users.

Test frameworks are simply a bit different from other library code, and 
I think the licensing should reflect this. But that's all down to Kostis 
and Manolis to decide, of course.


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