BETA_NC is a FORTRAN77 library, using double precision arithmetic, which evaluates the cumulative distribution function (CDF) of the noncentral Beta distribution.
ASA063 is a FORTRAN77 library which evaluates the incomplete Beta function.
ASA109 is a FORTRAN77 library which inverts the incomplete Beta function.
ASA226 is a FORTRAN77 library which computes the CDF of the noncentral Beta distribution.
ASA310 is a FORTRAN77 library which computes the CDF of the noncentral Beta distribution.
BETA_NC is also available in a C++ version and a FORTRAN90 version and a MATLAB version.
DCDFLIB is a FORTRAN90 library which evaluates and inverts a number of statistical distributions.
GSL is a C++ library which includes many routines for evaluating probability distributions.
PROB is a FORTRAN90 library which evaluates and inverts a number of probabilistic distributions.
TEST_VALUES is a FORTRAN77 library which contains sample values for a number of distributions.
TOMS179 is a FORTRAN77 library which evaluates the incomplete Beta function.
TOMS708 is a FORTRAN77 library which evaluates the incomplete Beta function.
You can go up one level to the FORTRAN77 source codes.