first compile and load the program

from UNIX do-actaully issue this command inside Splus given the syntax here
> !Splus COMPILE maxkapS1.c 

then in Splus do
> print(dyn.load("maxkapS1.o"))

then just supply a data matrix (need more than 5 clusters for the 
program to work as written)

> mm _ maxkappa(cldata[,1:3])

this returns the non-diagonal elements of the max kappa matrix

here is the S-Plus function

> maxkappa
function(datMat)
{
        ncl <- as.integer(dim(table(datMat[, 1])))
        if(ncl < 5) {
                cat("too few clusters")
                res <- 0
        }
        else {
                nunits <- as.integer(dim(datMat)[1])
                nmeth <- as.integer(dim(datMat)[2])
                ans <- c(1:c((nmeth * (nmeth - 1))/2))
                storage.mode(datMat) <- "single"
                storage.mode(ans) <- "single"
                res <- .C("clustComp",
                        ans = ans,
                        datMat,
                        nunits,
                        nmeth,
                        ncl)$ans
        }
        res
}

and you need the file maxkapS1.c in the directory from which you run Splus