From my understanding, when you purchase FCPX, if you have multiple machines, you can put it on up to 5 machines for the initial $299. My question is, does the same apply with Motion and other plug ins?

If that is not the case, then if on machine a I have all of the plug-ins, but need to go to machine b (as it is portable) and it has no plugins, when i open up the session will all effects be gone from the project?

Thanks guys!

It's not just FCP, it's the App Store policy. You can put any iTunes/App Store purchase on up to 8 or 10 Apple devices. 5 of those can be actual Mac computers. Applies to everything purchased on iTunes or the App Store.

All the devices (Macs, iPads, iPhones, iPods) must be "authorized" for your same iTunes/App Store account.

When you purchase plugins, those folks have their own policies they make up themselves. If it's sold on the App Store, it's the App Store policy. If it's purchased elsewhere, it's the developer's own policy.

Most let you install plugins on multiple machines to match the App Store's 5-Mac policy. But you'll have to manually install it on each Mac. It won't automatically install on multiple machines.