I would like to see this added too. Supporting an external R into which we can install arbitrary packages is an absolute necessity. Without access to R packages, there's little point in calling R from Mathematica at all.

I wrote a blog post about how to use external R installations on Mac (and other platforms), but the procedure is a bit messy:

• http://szhorvat.net/pelican/setting-up-rlink-for-mathematica.html

You can use it as a workaround until this gets fixed.

Thanks for the pointer to Horvat's material.

It's unclear if his method requires leaving SIP disabled. If so, then this rather awkward workaround would be unsatisfactory for me on security grounds. If not, then it's worth a try.

But still no excuse for WRI not having added support on platforms other than Windows.

@Marco: Just a note that if you patch libjri.jnilib, it is no longer necessary to set DYLD_LIBRARY _PATH. The whole reason why we need to patch this file is that with SIP enabled, DYLD_LIBRARY _PATH will no longer influence which shared libraries get loaded.