AmiPodder is an AREXX program, so you need to have RexxMast (found in the "System" drawer on your Workbench partition) running to use it. RexxMast seems to run by default on Amiga OS 4. I have tested AmiPodder on Amiga OS 3.9 and OS 4, and I have reports from betatesters and users that it works on MorphOS.
Please note that a problem has been reported with the timing of the automatic update and download check features on MorphOS only. Please leave these options turned off for the time being if you use MorphOS. For more details please check the Configuration section.
In addition you'll need to have the following supporting packages installed:
As long as you have RexxMast running, AmiPodder will display an error if any of the requirements are missing. If it lists missing libraries, this normally means you don't have rxMUI installed or the version you have is too old. To correct this, download rxMUI from its home page linked above, unarchive it and run the installer. When the installer asks "What do you want to install?" untick everything except "Libraries" and "MUI classes", then let the installer install the files in the default locations. This should be enough to get AmiPodder up and running. Note that you need to have MUI itself installed before you can install rxMUI.
If you are upgrading from an earlier version, select the drawer containing the AmiPodder drawer and the installation will be upgraded. For example if you had installed AmiPodder previously in Work:Utilities/AmiPodder then select Work:Utilities in the installer when upgrading. Your preferences and channels data file will not be overwritten. Newer versions of AmiPodder work with preferences files from older versions and update them automatically. Older versions should work with newer preferences and data files but this is not tested. So if you think you may want to go back to an earlier version, backup your AmiPodder.prefs and AmiPodder_channels.data files before upgrading.