The plugins work fine without a license. I do not cripple them in any way if you don’t activate the license. An active license is only needed for automatic updates, and to obtain support. So you really only need to activate on the site where you want to use automatic updates (perhaps the dev site for testing, and then push to the live site when you know it is working)
The “Single Site” license for all of my plugins actually allow you to activate the license on two sites/domains, specifically to allow you to install and test updates on dev/staging sites. Also, the licensing software I use doesn’t count some types of localhost domains towards your activation limit (again, for the same purpose)
If you need to delete an activation for a particular site, you can go to the Purchase History & Licenses page, scroll down to the licenses section, and click on the Manage Sites link for a license to deactivate a particular site/domain.