[Proj] Problem with projections that need support libraries

[Carl Godkin]

Gerald Evenden wrote:

> 
> The kernel is a little nasty but the adaptive integration procedure in gsl
> (Gnu Scientific Library) handles it nicely.
> 
> The problem is this: a libproj4 implementation would most easily be 
> performed
> by using the gsl routine by linking to the gsl library.  Extracting the 
> gsl procedures
> would be very, very tedious and error prone.  But by linking to the gsl 
> library
> transportation is compromised and/or complicated---especially in non-unix
> environments.
> 
> Note: there are other projections which are not implemented due to the fact
> that complex functions (often available in gsl) are impractical to 
> include as
> part of libproj4 source.
> 
> One option is to put compiler/Makefile switches that would exclude 
> projections
> that required exotic libraries.  Note: any exotic libraries would be 
> required to
> be freely available.

One issue to consider is that that GSL is available only with
the GPL (Gnu General Public License), not the LGPL (Gnu Library
General Public License).  This is a more restrictive license
than the rest of PROJ.4's MIT-like license.

As I understand it, use of the GPL (as opposed to LPGL) means that
we can't use GSL in proprietary/commercial applications.

So I'd rather have you keep the GSL components optional so we can
still use PROJ.4 in commercial applications.

Thanks,

carl