Versions 4.12 and newer
Starting with version 4.12, AxoSyslog is licensed under a single, clear open source license: GNU General Public License version 3 or later (GPL-3.0-or-later). For details on what this means, see the AxoSyslog License Update: Moving to GPL3 blog post.
Versions 3.2 - 4.11
Between versions 3.2 and 4.11, the AxoSyslog application was licensed under a combined LGPL+GPL license. The core of AxoSyslog was licensed under the GNU Lesser General Public License Version 2.1 license, while the rest of the codebase under the GNU General Public License Version 2 license.
lib directory of the source code package is under LGPL, the rest is GPL.
For details about the LGPL and GPL licenses, see GNU Lesser General Public License and GNU General Public License, respectively.
Documentation license
The Documentation is licensed separately from AxoSyslog. For details, see The syslog-ng OSE Documentation License.