To make it easy for proprietary data licensees to present the data they have bought in OpenLayers.Layer directly, e.g. by using the WMS layer or an adaptation of that to their own tiling scheme, we need to add methods of obeying the attribution and copyright requirements of these data sources. Typically a line of text at the bottom of the map window is sufficient.
Since maps contain many layers, the attribution text must be able to handle additions from many layers -- gracefully! The attribution text should also allow HTML so that it can contain hyperlinks, bolding, © etc.
A key requirement for most of the data providers that require attribution text is that it be visible when someone takes a screenshot. That means that the attribution text can disappear when data from that layer is not visible.
