The state of open licensing in 2017 – Open Knowledge International Blog

"Initial results from the GODI 2016/17 show roughly that only 38 percent of the eligible datasets were openly licensed (this value may change slightly after the final publication on June 15).

The other licenses include many use restrictions including use limitations to non-commercial purposes, restrictions on reuse and/or modifications of the data.  

Where data is openly licensed, best practices are hardly ever followed

In the majority of cases, our research team found governments apply general terms of use instead of specific licenses for the data. Open government licenses and Creative Commons licenses were seldom used. As outlined above, this is problematic. Using customized licenses or terms of use may impose additional requirements such as:

• Require specific attribution statements desired by the publisher
• Add clauses that make it unclear how data can be reused and modified.
• Adapt licenses to local legislation

Throughout our assessment, we encountered unnecessary or ambivalent clauses, which in turn may cause legal concerns, especially when people consider to use data commercially. Sometimes we came across redundant clauses that cause more confusion than clarity.  For example clauses may forbid to use data in an unlawful way (see also the discussion here)."