The Haala project and its artefacts (unless stated otherwise) fall under terms of the GNU Lesser General Public License (LGPL) version 3.
Why move from the GPL to the Lesser GPL?
Using the Lesser GPL permits use of an artefact in proprietary programs; using the ordinary GPL for an artefact makes it available only for free programs. In practice this means that you can incorporate an LGPL artefact in a proprietary project, however, if you modify its source code you are required to release that under the terms of the LGPL. More than that, the LGPLv3 is compatible with the APACHEv2 license.
The LGPL is flexible enough to allow the use of artefacts in both open source and commercial projects. The LGPL guarantees that artefacts and any modifications made to them will stay open source.
Importing artefacts' public interfaces in your Java code, extending them by sub-classing or implementation of an extension interface is considered to be dynamic linking. Hence this interpretation of the LGPL is that the use of the unmodified source does not affect the license of your application code. The use of the unmodified binaries of never affects the license of your application or distribution.
Submitting your modifications
If you modify artefacts and redistribute your modifications, the LGPL applies.
Please submit any modifications to email
GNU Lesser General Public License official web page
GNU Lesser General Public License explained
The list of the open source licenses supported by the Free Software Foundation
Apache License v2.0 and GPL Compatibility