If you are interested in moving CRM Online customizations over to an On-Premise deployment, you should read KB article 976978. A likely scenario for this is those that want to apply the Non-Profit customizations to an On-Prem instance.
The KB article describes processes and tools needed to update the xml to work in On-Prem. The summary is this:
On-prem code needs to be updated with Update Rollup 7 or later.
There is a MigrationProcessor Tool that strips out exclusive features in Online, like the Home Page, Charts, Help Visor, and Internet Marketing.
Otherwise, those trying to import Online xml into an On-Prem org will see the following error:
“Either the file could not be uploaded, or this is not a valid Customization file.”