Brute-force application to tests passwords for KeePass kdb files, kdbx are not supported. Only AES-encrypted files are supported at the moment. Key-files are not supported, but support for key-files is trivial to add.
The logic is deducted from file src/format/KeePass1Reader.cpp
(KeepassX-2.0-alpha source code), so it inherits the license: GNU GPLv2 / GPLv3