Buying a syslog-ng Premium Edition (syslog-ng PE) license permits you to perform the following:
Install one instance of the syslog-ng PE application in server mode to a single host. This host acts as the central log server of the network. You have to install the license file only on this host.
Install the syslog-ng PE application in relay or client mode on host computers within your organization (on any supported platform). You cannot redistribute the application to third parties. The total number of hosts permitted to run syslog-ng PE in relay or client mode is limited by the syslog-ng PE license. The client and relay hosts may use any operating system supported by syslog-ng PE. For details, see syslog-ng.com.
The syslog-ng Premium Edition license determines the number of individual hosts (also called log source hosts) that can send log messages to syslog-ng PE.
License grants and legal restrictions are fully described in the Software Transaction, License and End User License Agreements. Note that the Software Transaction, License and End User License Agreements and the Product Guide apply only to scenarios where the Licensee (the organization who has purchased the product) is the end user of the product. In any other scenario — for example, if you want to offer services provided by syslog-ng Premium Edition to your customers in an OEM or a Managed Service Provider (MSP) scenario — you have to negotiate the exact terms and conditions with One Identity.
A Log Source Host (LSH) is any host, server, or device (including virtual machines, active or passive networking devices, syslog-ng clients and relays, and so on) that is capable of sending log messages. Log Source Hosts are identified by their IP addresses, so virtual machines and vhosts are separately counted.
The syslog-ng Premium Edition application has three distinct modes of operation: Client, Relay, and Server.
In Client mode syslog-ng Premium Edition collects local logs generated by the host it is running on, and forwards them through a network connection to the central syslog-ng PE server, a relay, or another network destination. If you install the syslog-ng Premium Edition application in Client mode on a host, it counts as a Log Source Host, even if it does not send log messages to a syslog-ng Premium Edition server.
In Relay mode syslog-ng Premium Edition receives logs through the network from Log Source Hosts and forwards them to the central syslog-ng PE server, a relay, or another network destination. If you install the syslog-ng Premium Edition application in Relay mode on a host, it counts as a Log Source Host, even if it does not send log messages to a syslog-ng Premium Edition server.
Relays cannot store the received log messages in local files, except for the log messages of the relay host. Naturally, relays can use disk-based buffering for every message.
In Server mode syslog-ng Premium Edition acts as a central log-collecting server that receives messages through a network connection, and stores them locally, or forwards them to other destinations or external systems (for example, a SIEM or a database). Installing the syslog-ng Premium Edition application in Server mode requires a license file, this license file determines the number of Log Source Hosts that can send log messages to the syslog-ng Premium Edition server.
Note that the number of source hosts is important, not the number of hosts that directly sends messages to syslog-ng Premium Edition: every host that send messages to the server (directly or using a relay) counts as a Log Source Host.
If the actual IP address of the host differs from the IP address received by looking up its IP address from its hostname in the DNS, the syslog-ng server counts them as two different hosts.
If the number of Log Source Hosts reaches the license limit, the syslog-ng PE server will not accept connections from additional hosts. The messages sent by additional hosts will be dropped, even if the client uses a reliable transport method (for example, ALTP).
To make syslog-ng PE forget old clients that do not exist anymore, enable the reset-license-counter() global option.
If the no-parse flag is set in a message source on the syslog-ng PE server, syslog-ng PE assumes that the message arrived from the host (that is, from the last hop) that sent the message to syslog-ng PE, and information about the original sender is lost.
Starting with version 4 F1, the syslog-ng Premium Edition application is based on the syslog-ng Open Source Edition application, and includes elements that are licensed under the LGPL or GPL licenses. You can download the core of syslog-ng PE here. The components located under the /lib directory are licensed under the GNU Lesser General Public License Version 2.1 license, while the rest of the codebase is licensed under the GNU General Public License Version 2 license. External libraries and other dependencies used by syslog-ng PE have their own licenses, typically GPL, LGPL, MIT, or BSD.
Third-party contributions includes the text of the licenses applicable to syslog-ng Premium Edition.