The licensing agreement allows you to install on more than one computer, with the caveat that you can only RUN it on a single computer at a time.
So, you can have it on two computers, but wouldn't be allowed to have Sonar up and running on both computers at the same time.
They have operated on a trust level for decades now, and it is generally honored by folks out of respect for that trust. Other companies using dongles and single-machine licensing and all of that really has pissed off a lot of folks over the years, so that a company like Cakewalk allows for additional computers to have Sonar installed really is thought of as pretty cool by the users.
Bob Bone