Licences are considered to apply to 'distribution' (I'm not entirely
sure if that is what you mean by 'released'), but some also apply to
usage.
The primary requirements for distribution, especially over CRAN, are
that the licence be clear and usable. Examples of problems
- licences that prohibit distribution without further permission
- claims that some parts of a package are under one licence and other
parts under another, without making clear what licence applies to the
whole package.
- copying parts of the work of others (most often the R sources)
without acknowledgement and/or with an incompatible licence.
- licences which require the sources to be made available (e.g. GPL)
with some components without sources and no other evidence of
availability.
- incompatibility. If your package has licence A and 'Depends:' or
'Imports:' other packages with licence B, then you create problems for
users if A and B are incompatible. A recent example is a licence that
prohibited certain classes of users and another that prohibited any
restrictions on use.
See 'Writing R Extensions' for the requirements of the LICENSE field
in the DESCRIPTION file. Life is much simpler for the users
(including the CRAN maintainers) if one of the standard forms is used,
since automated checking is possible.
See also https://stat.ethz.ch/pipermail/r-devel/2009-May/053248.html
for a related policy statement from the R Foundation.
Ultimately the discretion is of those doing the distribution, e.g. the
CRAN maintainers (and I am not writing on their behalf).
On Fri, 29 May 2009, Nathan S. Watson-Haigh wrote:
> Are there any particular licences under which R packages must be
> released or is it the discretion of the author? The same question if
> the package is to be destined for CRAN?
>
> Kind regards,
> Nathan
>
> --
> --------------------------------------------------------
> Dr. Nathan S. Watson-Haigh
> OCE Post Doctoral Fellow
> CSIRO Livestock Industries
> Queensland Bioscience Precinct
> St Lucia, QLD 4067
> Australia
>
> Tel: +61 (0)7 3214 2922
> Fax: +61 (0)7 3214 2900
> Web: http://www.csiro.au/people/Nathan.Watson-Haigh.html
--
Brian D. Ripley, ripley at stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595