Javier Ángel Velázquez Muriel wrote: > I'm going to need a FFT library. Is FFTW a possibility (Daniel says > there are workarounds) or would you suggest something else?

It would be much easier to use one that has a permissive license - there is certainly no need to reimplement FFT since there are many many implementations already out there. See for example the "FFT Source Code" links at http://www.fftw.org/links.html. I guess it depends on what you want to use it for, but it may make sense to choose one of the public domain (PD) codes listed there that also performs well on the FFTW benchmarks.

Ben