As the title states can I download XenForo and install it on my laptop for plugin development with my existing license or do I need a separate license for it since it’s running on a different hostname (localhost)?
5. How many installations can I make with a single license?
Each license permits you to install the software once. However, you may create additional test installations for testing purposes only. Any test installation of this kind must be password protected, and access to it must be limited to you and your website staff. See the License agreement for the entire scope.
Note that test installations may show a message in the ACP as follows: "The Board URL option does not match the site URL configured for your license."
That message can't be disabled but it can just be ignored.