If you wish, you can download the source code R and compile the executables yourself. This is really only for an expert user, so to paraphrase r-project.org: "if you are not sure what compiling means, you most probably do not want to do this".
To make sure that RStudio can talk with the compiled binaries, you need to configure the Makefile using the --enable-R-shlib flag. So after downloading and unpacking the source tarball, change the directory to R2.XX.X, and type the following commands:
./configure --enable-R-shlib ma ke make install
