Hi OSMfan,
Une recherche sur SwissImage me conduit à la page http://www.swisstopo.admin.ch/internet/swisstopo/fr/home/products/images/ort...
L'orthophoto ayant été acquise auprès de Swisstopo, je ne suis pas du tout certain que l'on ait le droit de digitaliser de l'information au profit d'OSM sur cette base.
Did they buy the images from Swisstopo including the rights to release it under any licence they want?
First of all, IMHO that's none of our concern. If public authorities give a general permission to everyone to do something, it's their responsibility to make sure if they are allowed to grant this right. Not ours.
Secondly I know for example that in Zurich (the city), they sell their old pictures for half the price, every time they produce a new set. Swisstopo says that they produce new photos every three years, so the market value for pictures from 1998 would be about 1/16th or 6% of todays prices.
Given that, I won't have a guilty conscience.
Regards, Thomas