Hi Melanie, you might find this discussion useful too: http://scn.sap.com/thread/3209655
Seems like if you are a SAP Customer/Partner the SAPUI5 license is included in your existing agreement with SAP. If you are not then it is still unclear.
If I were you I would probably download the non-evaluation version from the service marketplace, esp. if you are an SAP partner or customer already.
Hth,
Simon