So my guess, is Apache and GPLv2 together makes sense if author wants to give the user the maximum choice in combining the library with other software. That because depending which lawyers you ask Apache and GPL are not always compatible.
So say your code is Apache and you want to use RocksDB, you can pick to use the Apache license for it. Your code is GPL, then you can pick GPL.
> Hi all, wanted to jump in here to let everyone know that the RocksDB team is adjusting the licensing such that it will be dual-licensed under the Apache 2 and GPL 2 (for MySQL compatibility) licenses.