hamsterdb is available under several licenses - Open Source licenses (GPL 2 and GPL 3, with several exceptions for other FOSS licenses) and a "commercial", closed source license.
The hamsterdb Commercial License allows customers to develop, use and
distribute their application under standard commercial terms.
The hamsterdb Open Source Licenses are available under the terms of the GNU
Public License 2 or any later version (or other FOSS licenses). If you use
the GPL license of hamsterdb , you are forced to release your own product
under GPL (or another open source license - see
and anyone using your software must have access to complete source code,
and must be able
to modify and redistribute that software to anyone free of charge.
"Quid Pro Quo"
The rule of thumb for hamsterdb licensing is: if you wish to derive a
commercial advantage by not releasing your application under the GPL open
source license, you must purchase an appropriate number of commercial hamsterdb
licenses. By purchasing commercial licenses, you do not longer have to release
your application's source code.
Open Source Licenses
The GPL licenses have a long history in the software development world. There
is a fair amount of explanations and comments in the web. The GNU project
has assembled a list of frequently asked questions and their answers at
Read the GPL 2 »
Read the GPL 3 »
Read more about FOSS exceptions »
The Commercial License
Commercial licenses are sold "per developer". If a company has three developers
working with hamsterdb , and does not want to follow the rules of the
Open Source licenses, it has to buy three Commercial Licenses.
The term "Commercial" is a bit misleading - the GPL Licenses can also
be used for commercial software development; however, it is not typical, and
therefore we use the term "Commercial" to distinguish between Open Source and
Close Source licenses.
Read the hamsterdb Commercial License Agreement »
For legal reasons, you can find a German translation of the Commercial License Agreement here: hamsterdb Kommerzielle Lizenz-Vereinbarungen »