No browser. Again, it could be a proprietary binary executable, totally distinct from Easel.
How would this deny anyone of any functionality? Assuming the concept were feasible, it would constitute an option that we members of the Inventables community don't currently have; that is, to sell our designs over the wire without necessarily having to manufacture or ship anything.
You're given a limited time period to use the design. You produce as many copies as you want during that period. I don't see this as an issue so long as a given customer understands the terms of the transaction agreement.