Generated map tiles are "produced work" and don't have to be licensed under ODbL. If they make their (raw) data available as download would it have to be under ODbL.
Explained in 3b and 3c on http://wiki.openstreetmap.org/wiki/Legal_FAQ
Explained in 3b and 3c on http://wiki.openstreetmap.org/wiki/Legal_FAQ
4.6 Access to Derivative Databases. If You Publicly Use a Derivative
Database or a Produced Work from a Derivative Database, You must also
offer to recipients of the Derivative Database or Produced Work a copy
in a machine readable form of:
a. The entire Derivative Database; or
b. A file containing all of the alterations made to the Database or
the method of making the alterations to the Database (such as an
algorithm), including any additional Contents, that make up all the
differences between the Database and the Derivative Database.
The Derivative Database (under a.) or alteration file (under b.) must be
available at no more than a reasonable production cost for physical
distributions and free of charge if distributed over the internet.