Coincidence! I've just been putting together an R client for BioGRID. Very rough initial version is at https://github.com/rajarshi/cdkr/tree/master/rbiogrid. To install
library(devtools) install_github("cdkr", "rajarshi", subdir="rbiogrid")
You will need to get an access key from the BioGRID website. Right now it has no tests and has basic functionality to get interactions by gene names. It sets a number of arguments by default (e.g., selfInteractionsExcluded = TRUE, includeInteractorInteractions = FALSE) - you can view the source of the function to see them.
Example usage is
library(rbiogrid) set.access.key('XXXX') get.interactions('PLK1')
yes, use the REST service http://wiki.thebiogrid.org/doku.php/biogridrest and the R methods to access the web http://www.math.ucla.edu/~anderson/rw1001/library/base/html/read.table.url.html