I completely agree with you that this buzzword bingo has to stop.
However you seem to also have messed up the terminology a bit. :)
Cloud computing refers to provisioning of resources across the network normally using virtual machines. You retain "full" control of the machine. Cloud computing could be used for distributed computing.
Grid computing is the connection of supercomputers across the world. This involves things like handling access rights, policies, accounting etc.
Parallel computation involves the computation of a problem spread out over several processors.
Distributed computing is like parallel computation, but distributed across several machines. It therefore has to take into account things such as network latencies, machine failures etc.
Volunteer Computing involves harnessing the power of resources donated by the public. This can be a form of distributed computing, but not necessarily. BOINC is a good example of this.
Their project obviously falls into the last category, and has nothing to do with either Grid or Cloud. Their main difference from BOINC is the ability to run directly in the browser. This is hardly a new idea, and I remember projects like this from at least back in 2003. As far as I can see from the documentation, software such as MiG has been able to do all they do and much more since 2005. I'm a bit disappointed that Oxford Uni is not more innovative and get the terminology wrong, but it is the Physics department so let's cut them some slack. :)
Disclaimer: I'm a researcher in distributed computing particularly Grid and Volunteer Computing.