There used to be some on the web site, but it got so out of date I removed it. I'll add some updated instructions when I get some time, but it's really very simple. All you have to do is:
1. Grab the latest JDK if you don't already have it (note that you really only need a 1.4 JDK to compile, but there's no reason not to use the latest) - http://java.sun.com/javase/downloads/index.jsp
2. Get Apache Ant if you don't already have it (http://ant.apache.org/
3. Download the latest RText source from SourceForge - http://sourceforge.net/projects/rtext
4. At a command prompt, cd into the directory in which you unzipped the RText source code. Type "ant" and hit Enter. This kicks off the default target in the ant build file build.xml, which builds RText.
5. When this completes, you should have RText build in a "dist" subdirectory.
Simple as that!
Let me know if you have any problems along the way.