From AMule Project FAQ
Multiplatform refers to the ability of an application to be run successfully on different platforms (a platform is the combination of hardware with it's installed operative system and it's main configuration).
That is, a multiplatform application such as aMule, can be successfully run on different operative systems such as Windows, Linux or Solaris, and on different hardware configurations such as standard x86 computers, new AMD64 processors or even Sun's SPARC systems.
Currently (known) supported operative systems include:
Currently (known) supported processors include: