You install Opus on your main PC first. Then, you use the internal export tool to create a "Portable Edition" on a USB stick or removable drive.
Directory Opus does not use a standard alphanumeric serial key for activation; instead, it uses a , which is a small text file you must install via the License Manager. For portable use, the software allows you to "export" a licensed copy to a USB drive, which carries the license with it. Licensing System Overview directory opus license key portable