Install R extension

I tried to install R extension through Marketplace, however, that didn't work because of proxy setting.

Then I read something about downloading the jar file from here: http://sourceforge.net/projects/rapidminer/files/2.%20Extensions/
and copying into the 'plugin' folder.

My question is that there are three additional files listed for R extension:
src.zip, javadoc,zip and installer.exe
Do we need all these four files? Or one jar file is enough?

Thanks.