[_deh]

To expand on the free point - it's not just that SAS and SPSS have a price tag. You're then supposed to pay for a load of bolt-on modules. The extreme case is if you want to do decision trees in SAS, they've made a commercial decision that you must be doing some kind of 'Enterprise-Grade Data Mining', and therefore need to pay their 5-figure price tag rather than their 4-figure price tag.

I think this has been a big barrier to any sort of package ecosystem to rival CRAN. Even if your entire target audience has SAS or SPSS, if your new package depended on one or more of those modules, it's going to cost some of your prospective users hard cash to run it. Whereas R just installs the dependencies for you.