- Set up a free account with Apple's ADC.
- Download and install Apple's Java 1.4.1 DP9 from the ADC site.
- Download the generic Unix tarball of IDEA from www.intellij.com.
- Unpack it ... the directory that is created will be known as IDEA_HOME.
- Create a directory named jre in IDEA_HOME. ie: IDEA_HOME/jre.
- Create a bin and lib directory in the jre directory. ie: IDEA_HOME/jre/bin and IDEA_HOME/jre/lib.
- Copy the contents of /System -> Library -> Frameworks -> JavaVM.framework -> Versions -> 1.4.1 -> Commands to the IDEA_HOME/jre/bin directory.
- Copy /System -> Library -> Frameworks -> JavaVM.framework -> Versions -> 1.4.1 -> Home -> src.jar to the IDEA_HOME/jre/lib directory.
- Run the IDEA_HOME/bin/idea.sh script in the terminal and you're good to go.
[Editor's note: I haven't tested this one myself, though I am grabbing the new DP9 Java release as I type this...]

