I don't think it's behind a paywall; it's CC licensed. I can access it and I'm not connected to an academic network at the moment.
On a broader note, there's a big push for open access at the moment (as there should be), so there's no longer a need to assume that a paper is behind a paywall just because it's on a journal's website anymore.
On a broader note, there's a big push for open access at the moment (as there should be), so there's no longer a need to assume that a paper is behind a paywall just because it's on a journal's website anymore.