Yes you can test it on multiple sites. It is unlimited. Review #3 on the Features page - http://www.studiopress.com/features
3. Genesis Gives You Unlimited Everything
You get unlimited support. Unlimited updates. Unlimited websites. There’s no “Developer Option” here. One low price entitles you to unlimited support, updates, and domains you can build on. If you’ve got multiple websites (or client projects), Genesis offers unparalleled value.
And when you want answers to questions about your site, you want them now. That’s why we give you lifetime access to our world-class support team and forum. Our team consists of over 20 moderators from all over the world, who provide solutions and help to our 63,000+ members. We’re here today and tomorrow, whenever you have a question.
One of the many reasons I choose Genesis!