Hey @dbinbrea,
There unfortunately isn’t a way to add a new domain to the license, but the good news here is that a license isn’t really required for the dev site to being with. The reason for this is that the license is NOT required for anything in the plugin to function – it works 100% completely normally without a license key.
The license key simply alerts your site of an available update, and lets you access customer support here on the Premium forums.
But if you have the License active on the Live site, then you’ll learn of Updates there – and you can then just manually download the latest version of the plugins here on this site at http://theeventscalendar.com/my-account/downloads
And we can happily support both the live site and its development version 🙂
I hope this information helps clarify things a bit, and that this is indeed a satisfactory process for you. Let me know if that’s the case and/or if there’s anything else I can help with!
Cheers,
George