Right now there are two ways to install the extension:
From the zip file. After downloading Snapfont from Gumroad, you'll get access to a zip file.
Read the instructions here to install from a zip file. We generally recommend this method if you want the latest version of Snapfont.
From the Chrome webstore. Head over to the Chrome webstore and install from there. This is the quickest method of installing Snapfont, but this version of Snapfont may be old as Chrome webstore takes 2-3 weeks to put the extension on the store.
While Snapfont will eventually be a paid plugin, the old license key you got in your Gumroad email will still work with future updates.
This is done as a way of thanking the early supporters who used Snapfont.
So no, you won't need to get a new license key for future updates.