I have an entry here about how to install JAGS and rjags in Fedora. However, I have exchanged emails with Robert Dorazio and Dr. Martyn Plummer. Here are the easier steps to compile JAGS and install rjags in R.
1. After you extract the source code of JAGS, go to the folder where the JAGS makefile is using a terminal.
2. In a terminal, type the following
sudo ./configure –prefix=