Oracle has changed the license of its embedded database library, Berkeley DB. The software is widely used as a key-value store within other applications and historically used an OSI-approved strong copyleft license which was similar to the GPL.
Under that license, distributing software that embedded Berkeley DB involved also providing "information on how to obtain complete source code for the DB software and any accompanying software that uses the DB software."
Now future versions of Berkeley DB use the GNU Affero General Public License (AGPL). This says "your modified version must prominently offer all users interacting with it remotely through a computer network ... an opportunity to receive the Corresponding Source of your version."
This will cause some problems for Web developers using Berkeley DB for local storage. Compliance has not really been an issue because they never "redistributed" the source of their Web apps.Now they will have to make sure their whole Web app is compliant with the AGPL and make full corresponding source to their Web application available.
They also need to ensure the full app has compatible licensing. Practically that means that the whole source code has to be licensed under the GPLv3 or the AGPL.