You can try out a Rack Extension by going to the Propellerhead web shop at shop.propellerheads.se and using the "Try" function. This gives you a trial license which will last for 30 days. During this time, the Rack Extension is fully operational, but requires that you run Reason Essentials with Internet Verification, see “Running Reason Essentials with Internet Verification”.
When the trial license expires, the Rack Extension will be removed from the program menus. However, it will remain installed unless you manually uninstall it. Should you choose to purchase the Rack Extension later on, you don't need to download it again.
When you purchase a Rack Extension, a license is automatically written to your Propellerhead user account on the Propellerhead web site. Just like with your Reason Essentials license, you can write a Rack Extension license to your authorized computer or Ignition Key (or Propellerhead Balance audio interface). You can download and install the Rack Extension on as many computers as you like. However, to use the Rack Extension in Reason Essentials you either need your authorized computer, your Ignition Key hardware with the Rack Extension license on it, or an Internet connection to run with Internet Verification.
If you move to another computer, you can download and install all your Rack Extensions by going to your user account on the Propellerhead web site (Your Products page, Rack Extensions tab) and clicking "Sync All". This function is also excellent for making sure you got the latest versions and updates of all your Rack Extensions. Only files that are missing on your computer will be downloaded and installed.
Rack Extensions can be updated, with fixes and additions. Updates are posted on your Propellerhead user account page. An update can be free or paid. In both cases, the Rack Extension is backwards compatible, meaning that you can open older songs and patches and they will sound the same.