I read the license/contract. It is enforceable much like the GPL if the data is copyright. It is significantly weakened if the data is not copyright and you're in a place with no concept of "database rights" (e.g. the USA.)
The lawyers who wrote the ODBL understand this issue: check out how they define the word 'use' in section 1.
The lawyers who wrote the ODBL understand this issue: check out how they define the word 'use' in section 1.
IANAL, yadda yadda.