OK,  I thought the license file was required, but clearly it is not. So, I used the OSUpdate Package Builder to create the APF.  But, when I try the Rapid Deployment (using MSP 3.3.1), it gives me this error: Upgrade Aborted "Update Package is corrupted!! Make sure the upgrade package is not tampered." I've tried recreating the apf again from scratch and uploading it to MSP via the PackagesToInstall folder and created a new Bundle and staging profile.  But, it still gives me the same error message. Any ideas on what I might be doing wrong? Is this an issue with MSP or the OS Package Builder?

You should really contact the help desk for assistance since they can work with you one on one and go step by step with you to verify what you are doing.  It could be related to the version of the OS Update Package Builder you are using, the contents you are including into the Package, or something going on with MSP or your Relay Server.  I have never seen the error you are describing.  Can you tell if it comes from the RD Client or the OS Update Utility?  Their UIs are totally different, so it should be easy to tell which it is from.

As this question was raised more than three months ago, I don't know if you're still looking for a solution, but you can use the AirBEAM Package Builder or MSP Package Builder to create your OS downgrade package. I would not recommend to use the OSupdate package builder, because the process for upgrading/downgrading an OS is different from a regular firmware installation. Simply add all the files from the ZIP file to the package, and have them downloaded to the \Temp directory on the device. For example, for the file 55x4w61LenOS023500.sig.gz the client filename should be \Temp\55x4w61LenOS023500.sig.gz. Make sure the file type is set to Download for each file. Next, set the Alternate Storage for the package to \Temp, and the Install Command to \Temp\WM6_Update.exe. Generate the APF file, upload it to MSP, and create a bundle and staging profile for it.

It is really up to the device team to determine if the downgrade you are trying to do is supported or not.  Given that they provided files that would seem to be aimed at doing that, chances are good that it would be supported, but it may be limited as to which hardware it can support.  It is always best to post on an appropriate Mobile Computing Forum and get confirmation whenever you are doing something somewhat off the main line.  If they tell you it can be done, then it probably can also be done with an APF. The next thing to consider is what tool you are going to use to process the Package.  AirBEAM has been end of life since Jan 1, 2011, although it may be in the device.  You CANNOT use AirBEAM to deploy an APF unless either the AirBEAM Client or the APF is licensed, and we no longer sell new AirBEAM licenses.  So, using AirBEAM is likely not a viable option.  You can use the RD Client that is present in the device, but that requires access to an MSP Server.  When using the RD Client and an MSP Server to deploy an APF, the APF does NOT need to be licensed, and you can just ignore the prompt in the Package Builder that asks for a license. In most cases, we recommend using the OS Update Package Builder to build an APF to do an OS Update because it knows the best way to do it for every device.  But if you know what you are doing, you CAN build a workable OS Update Package using the regular Package Builder.  But then you need to know exactly which files are required, where they should be stored in the device, and how to initiate the update.  The location in a Windows Mobile device at which OS Update files should generally be loaded in \Temp.  But if the device has a lot of data stored in it, there may not be room and you may have to remove some data before the files will fit.  If that is the case, the same thing would have happened with an APF built using the OS Update Package Builder. What you may want to do is request that a downgrade APF be provided.  You could request that in the appropriate Mobile Computing Forum.  Then you would have an APF that was known to be working.  Otherwise, you might want to call the help desk to get assistance with rolling your own.