Dr Weiner has two arguments on that page:
(1) the routines in NR are old and outdated (I imagine most people have the 1992/1996 versions, though the books were updated in 2007)
(2) the NR routines given in the book are copyrighted which means you cannot distribute the source of a code that has NR routines in them to people who do not have the NR license (though you can distribute the binary of the code)
I have never really paid attention to the content copyright pages, so I took a look of my copy of Numerical Recipes to find the following:
...These [diskettes] provide demonstration programs that illustrate the use of each subroutine and procedure in this book. They too can be ordered in the above manner.Now, I am no copyright law professional, but it seems like I can write a code with some functions/subroutines based on NR without trouble.
Unlicensed transfer of Numerical Recipes programs from the abovementioned IBM PC or Apple Macintosh diskettes to any other format, or to any computer except a single IBM PC or Apple Macintosh or compatible for each diskette purchased, is strictly prohibited.
In any event, there are alternatives to Numerical Recipes codes that are more up to date and free. I already mentioned LAPACK at the top of the page, but there is also:
SLATEC -- a large collection of routines such as ODE solvers, numerical integrators, and so on (it was partially re-written in F90 by John Burkardt, see here)
BLAS -- Basic Linear Algebra Subprograms, this is included in the SLATEC package, but is available separately
FGSL -- Fortran interface to the GNU Scientific Library (GSL)
MINPACK -- collection of non-linear equation solvers
I know that some of my colleagues use external libraries (GSL in particular), but I have yet to use any of them. I am somewhat curious about using LAPACK and SLATEC, but I will have to see if I can employ it beyond teaching a lecture or two on it for my class.
I can understand Dr Weiner's argument: why use routines that you have to pay for and are very restrictive in sharing when you can get it free from someone else without any restrictions? And I completely agree, however, I will not be boycotting Numerical Recipes because it is still a fantastic source of information for beginning programmers.
Comments are welcome!