[OSM-legal-talk] Mixing ODbL and CC-BY-SA databases

[Richard Weait]

On Sat, Jul 17, 2010 at 6:54 PM, Frederik Ramm <frederik at remote.org> wrote:
> Hi,
>
>   here's an interesting one.
>
> Suppose OSM has just changed its license to ODbL. A final CC-BY-SA planet
> has been released, non-relicensed data has been removed from the servers,
> and the project is again humming along nicely (relief!).
>
> Now I would like to make a slippy map overlay where areas are coloured red
> or green or different shades in between according to how much data is
> missing from the current ODbL dataset compared to the old CC-BY-SA data set.
> The idea being, if an area is red, it may be worth going there and
> resurveying the area because edits have been lost.
>
> I wonder if this is possible at all. Behind the scenes, I would have to
> compare the old CC-BY-SA data with the new data set to find out what
> happened. My tiles would be a derived work from the CC-BY-SA data set and as
> such licensed CC-BY-SA, no problem there. However, I would in all likelihood
> be creating an interim database derived from the new ODbL data set and the
> old CC-BY-SA data set. ODbL would require that I release that database under
> ODbL. But CC-BY-SA requires that if I release the database it must be under
> CC-BY-SA exclusively. Thus I cannot release the database, thus I cannot
> publish the tiles.

Or you create a thin-line style and render both tile sets without a
background color One set red, one set green, both 50% transparent.
Then you allow the user to combine the two tile sets, one over the
other, in the browser.

You don't compare or mix the data bases.  The user is looking at
produced works, ccbysa for the ccbysa tiles, your choice for the ODbL
tiles.  And the user has the option of republishing the overlay as
long as they follow your licensing requirements.  Or, just use them
for personal reference and go mapping.

How hard was that?  Frederik posts many wonderful hypothetical situations.  ;-)