OpenWrt is free software, provided AS-IS and without any warranty.
If not otherwise stated in the source files, the OpenWrt build environment is provided under the terms of the GNU General Public License Version 2. The exact GPLv2 license text can be found in the file LICENSE in the source repository.
The OpenWrt distribution (precompiled images etc.) bundles a lot of third party applications and modules which are available under various other Open Source licenses or Public Domain. The sources for those packages can be found on the OpenWrt source archive. Please refer to these source packages to find out which license applies to them.
We expect that you are knowledgeable about GNU/Linux and basic networking concepts, before you install OpenWrt on your router. Support may be provided on a voluntary basis by developers and fellow users, but is not guaranteed.
OpenWrt has joined The Software Freedom Conservancy (SFC): openwrt_joins_conservancy. They zealously pursue GPL violations that are reported to them, and if you're aware of one, please do email them at compliance@sfconservancy.org immediately.