[nly]

> CppDB on the other hand is MIT or Boost. It is the best DB library I found so far for C++.

Have you evaluated Code Synthesis's ODB?

[CCs]

> Have you evaluated Code Synthesis's ODB?

I did not test ODB yet, but I'm planning to. Not fan of their license tough...

[muyuu]

Are these key-value DBs like LevelDB / BerkeleyDB / etc? or maybe something more sophisticated?

[CCs]

Both CppDB and ODB are abstraction layers between your code and SQL (Postgres, mySQL etc). ODB is somewhat closer to ORM.

CppDB uses MIT or BSD license (you pick), ODB is under LGPL or commercial license.