The Syslog-ng Store Box license allow those who are in possession of a valid SSB license, to download syslog-ng Premium Edition free of charge. The only limitation of this use-case is that the syslog-ng Premium Edition installers acquired this way are limited (by the terms of the SSB license) to be only used in the relay and logging agent roles. This also means that you will not be supplied with a license for these syslog-ng Premium Edition instances. Syslog-ng Premium Edition will work without a license file in the above mentioned relay and logging agent roles.
Here is the excerpt from the SSB Administrator's Guide:
Buying a syslog-ng Store Box (SSB) license permits you to perform the following:
* Deploy one instance of the syslog-ng Store Box appliance as a central log collector server.
* The syslog-ng Store Box license also allows you to download the syslog-ng Premium
Edition application (including the syslog-ng Agent for Windows application) and install
it on hosts within your organization (on any supported platform) to use it as a log
collector agent (client) for syslog-ng Store Box. You cannot redistribute the
application to third parties.
* If you have bought a syslog-ng Store Box relay appliance, you can use it as a relay to
forward log messages to your central SSB server, a relay, or another network
For further information see the Licensing model and modes of operation Section of the Admin guide