There is a note in the requirements for Macromedia Flex  that it requires Tomcat 4.1.29 or higher. The version of Tomcat that comes on the Apple Xcode CD with OS X 10.3.3 is version 4.1.24 – so far it seems to work OK with Flex, but I figured I would go ahead and upgrade to avoid any potential problems. Rather than download the source and compile 4.1.29, I found an easy way to update to Tomcat 4.1.29 tonight with a prebuilt binary straight from Apple, no compiling neccessary. Apple released an Application Servers Update 2.0  for Mac OS X 10.3 server in late March, and lo and behold it contains updates for WebObjects, JBoss and Tomcat. Now the installer wont run unless its being installed on a copy of Mac OS X 10.3 Server, unless you tweak the install script, or in my case use a tool called Pacifist  to extract the binaries right from the installer. Here are the steps I took:
1) Download and install Pacifist 
3) Once you have grabbed the update and the disk image is mounted, open the package with Pacifist and extract the Tomcat folder.
4) Shutdown your existing copy of tomcat if its already running:
5) If you have any installations in the tomcat webapps folder, (in our case flex, flexsamples) or any customized configs for tomcat or other modifcations, move them out of the old tomcat folder located at:
and set them aside
6) Rename the old tomcat directory in case you need to restore it or grab anything from it.
7) Move the newly extracted tomcat folder from the Application Servers Update 2.0  package to the location of your original tomcat installation.
8) Drop your flex and flexsamples webapp folders into the new tomcat webapp folder
9) Start the new tomcat:
You should now be running Tomcat 4.1.29 – test this out by going to http://localhost:9006/ and look in the top left hand corner of the screen. Then try out your Flex apps to see if everything is working.
Your all set – now back to playing with Flex. See this previous entry  if you are looking to get Flex installed on OS X 10.3.3