IMT stands for Interoperability Matrix Tool. It is available on the NOW site.
In short, you can enter the config details of your host (ex. OS, protocol, HBA), what ONTAP version you are using, etc and then use a feature of the tool called end-to-end views to determine if your config is supported across SAN - SDU - SMO.
There is help available as well as some videos of how to use it should you need them.
So there is not confusion, the product you are referring to as SnapManager for Linux is called SnapDrive for Unix; and yes you are correct, SDU is required in order to run SMO.
-Mark