There is nothing that restricts the display of a proprietary data layer on top of an OSM render : in the resulting mashup, the variously licensed sources of data each remain in its own layer and there is therefore no mixing of conflicting licenses.
On the other hand, if you produce new data by processing OSM data or mixing it with your own, then you are constrained by the bounds of Openstreetmap's license.
> On the other hand, if you produce new data by processing OSM data or mixing it with your own, then you are constrained by the bounds of Openstreetmap's license.
.. such as the moment you provide a function to generate PDF versions of the maps, or any number of other features that end up mixing the data. So in effect you either accept severely limiting your features, or you use other sources of map data.
No - as long as the other items have no dependency on or interaction with the OSM layer, the generated PDF is clear of license conflict: it is still merely a composite display of independent sources, not a work produced on the basis of OSM data. If the OSM data was rendered without modification then it is not necessary to release the other data sources. Cf. http://wiki.openstreetmap.org/wiki/Open_Data_License/Use_Cas...
They've changed their tune then, because that used to be explicitly called out as an example of a grey area in the old license that they would be prevented with the new license.
If that's correct then that's fantastic.
Given that it's contradictory to what used to be claimed, it still makes me concerned about touching it without having a lawyer going over the license in great detail, though...
On the other hand, if you produce new data by processing OSM data or mixing it with your own, then you are constrained by the bounds of Openstreetmap's license.