A big difference from a CC-SA licence is that it is possible to make a produced work from OSM data and all you have to do is attribute OSM, there is no share-alike requirement. In this way, the OSM ODbL is less restrictive than a standard share-alike licence.
The main example of that is making a map image. You can make a map image from 100% OSM data, and that image doesn't have to be share-alike.
If you create a database as is the case of FreeGeoDB (and perhaps if you use OSM to geocode another database), then share-alike applies.
I don't understand. If I produce a map image with all the details I'm interested in, and publish it, then use opencv to extract the data from that image into a database, would I be free to license the resulting database as a I wish?
I don't know. Ask a lawyer or judge. You can read the licence http://opendatacommons.org/licenses/odbl/1.0/ and look at the definitions of "Produced work" (a map) or "Derivative Database".
In practice, no-one's really done that or likely to do it. Either you'd do something silly like make the map a SVG with all data encoded as textual attributes and your "Computer Vision Algorithm" is basically grep (in which case it would probably be seen as a Derivative Database), or do real CV on a real image, which is very hard to do and will result in bad results. It's sufficiently hard that no-one's worried about it.
If you really don't like the OSM licence, you are free to go to another map data provider, pay them what they charge and agree to whatever they want, and get something else. If you want OSM, agree to OSM's terms.
A big difference from a CC-SA licence is that it is possible to make a produced work from OSM data and all you have to do is attribute OSM, there is no share-alike requirement. In this way, the OSM ODbL is less restrictive than a standard share-alike licence.
The main example of that is making a map image. You can make a map image from 100% OSM data, and that image doesn't have to be share-alike.
If you create a database as is the case of FreeGeoDB (and perhaps if you use OSM to geocode another database), then share-alike applies.