According to MacTopia:
http://www.microsoft.com/mac/downloads.aspx?pid=download&location=/mac/download/ misc/messenger603.xml
** Messenger for Mac 6.0.3 makes it easy to take advantage of the full power of instant messaging, and it is a Universal application built to run on both PowerPC-based and Intel-based Macs. If you encountered a sign-in issue with Messenger for Mac 6.0, you should upgrade to Messenger for Mac 6.0.3.
To use Microsoft Messenger for Mac 6.0.3, your computer must meet the following minimum requirements:
Operating system: Mac OS X version 10.3.9 or later
Network access: Microsoft Office Live Communications Server 2005 (corporate accounts only)
Hard disk: 20 MB of hard disk space
Display: 1024 x 768 or higher resolution displaying thousands of colors
Internet access: Internet access might require you to pay a separate fee to a service provider; local and long-distance telephone charges might apply.
Important Make sure that your Mac OS X user account has read and write access.
Looks like it will be compatible with your "all" of your Macs.
Carolyn 🙂
