[erlang-questions] A PropEr announcement

[Richard Carlsson]

On 2011-06-16 08:43, Max Lapshin wrote:
> Of course, tests aren't covered with the same license.
>
> GCC is licensed under GPL. You are writing C code, which has ifdefs
> for GCC and for MSVC. How can you imagine, that someone will order you
> to release your program under GPL?
>
> PropEr is just a tool. If you distribute this tool, you must share
> sources. You may sell it, but with opened sources. But you don't have
> any restrictions about files, that this tool works with.

This is pretty simple: to a compiler, the source code you write are just 
input, and the resulting object files are just output, and these are not 
affected in any way by the licensing of the compiler itself, just like 
editing a photo in GIMP has no legal implications on the resulting image 
file.

There is one exception: if the generated object code contains 
significant portions of code copied from templates that belong to the 
compiler - then the license of the templates applies to the generated 
object code. The GNU Bison parser is such a case: see 
http://www.gnu.org/software/bison/manual/html_node/Conditions.html#Conditions 
for their explanation of how they originally used GPL for the template 
code as well, but later dropped that so it could be used freely by anyone.

(This also applies to code fragments in included header files - the 
guideline is that macros of up to 10 lines of code are not considered 
significant, but if they are larger, the author of the header file 
should consider adding an exception to the license - I have done that in 
EUnit - or use different licensing for the header files in order to 
avoid tainting users' code.)

But in a test framework, you often write code (your tests) which calls 
out to the test framework library code. In this respect, test code is no 
different from, say, scientific code that calls a math library. The 
resulting code, after linking (statically or at run-time) is a work 
based on the code of the test framework.

I guess that if the test code is written solely as callbacks, as done in 
the Common Test style of test suites, the situation is less clear.

     /Richard