Nah, you need to be online to purchase it of course, but after that the credentials are saved to your computer so you can run the software without being online. Same way the current eLicenser works basically… you need to go online to first set it up but after that you are good.
Steam is just software on your computer, no different than the eLicenser software we already have to install.
Cakewalk SONAR is on Steam.