On how many devices can you install a paid app purchased from the Amazon App Store?

Several questions on Android Enthusiasts (including [this one])1 seek to determine on how many different Android devices an app purchased from the Google Play Store can be installed. The answers provided state that the answer is "unlimited".

What about applications purchased from the Amazon App Store? Are there limits to the number of devices on which the app can be installed. Or is it unlimited as well?