@tomww points out that the Spec Files Extra (SFE) repository is packaging recent node.js versions, built with their GCC 4.6.3 compilers. That means installation is as simple as a pair of pkg(5) invocations

# pkg set-publisher -p http://pkg.openindiana.org/sfe
# pkg install runtime/javascript/nodejs

The current version is 0.8.16, built less than 24 hours ago. Cool.