After several requests, I've decided to make the source code for voidfinder publicly available (to download it, please click here). The code has been extensively tested, but I do not promise it is bug-less as it is a fairly clunky and long code. Please email me at cfoster@eso.org if you find anything awry with it or if you have any questions.
Basically, Voidfinder is a (very long) subroutine that takes the position of galaxies in cartesian coordinates. Some subroutines used in the body of SDSSvoidfinder (the main program) are used to convert the ra, dec and redshift into comoving cartesian coordinates that the subroutine voidfinder understands. The shape computing is also included in this file. So modulo formatting of the input file, this should work pretty painlessly (but slowly :P). Please pay attention to Lines 271 and 272 in order to select the proper case appropriate for your survey. More general information can be found here.
If you find voidfinder useful to your research, an acknowledgement will be appreciated and sufficient!
Happy finding and quantifying "nothing"!
P.S. It has been reported to me that the code may not compile under gfortran,
so another fortran compiler may be needed. This has to do with the
".not.eof(??)" expression which may be unknown to gfortran...