The package greenbrown was developed since the R version 2.15.3. To install the package directly from R-forge you need the most recent R version.
To install the most recent version of greenbrown type directly within R:
install.packages("greenbrown", repos="http://R-Forge.R-project.org")
If you want to use greenbrown, you have to load the package at the beginning of each R session with:
library(greenbrown)
You get during the installation a warning like this one?
Warning message:
package 'greenbrown' is not available (for R version X.Y.Z)
This message indicates that the most recent version or any updates to the greenbrown package were not yet build to a package. R-forge is a development platform and greenbrown is continously developed. Therefore it can often happen that the package needs to be checked and re-build. The package cannot be directly installed with install.packages during this stage. If you still want to use the package, you can download a *.tar file with an older version of the greenbrown package.. Then you can directly install the package from the *.tar file within R:
install.packages("greenbrown_2.4.2.tar.gz", repos = NULL, type="source")
greenbrown, Matthias Forkel, 2016-12-20