Lua is free software distributed under the terms of the MIT license reproduced here. Lua may be used for any purpose, including commercial purposes, at absolutely no cost. No paperwork, no royalties, no GNU-like "copyleft" restrictions, either. Just download it and use it.
The spirit of the Lua license is that you are free to use Lua for any purpose at no cost without having to ask us. The only requirement is that if you do use Lua, then you should give us credit by including the copyright notice somewhere in your product or its documentation. A nice, but optional, way to give us further credit is to include a Lua logo and a link to our site in a web page for your product.
Before Lua 5.0, Lua used its own license, which was very close to the zlib license and others, but not quite the same. Check the source distribution for the exact license text for each version before Lua 5.0. Nevertheless, if you wish to use those old versions, you may hereby assume that they have all been re-licensed under the MIT license as described above.
Copyright © 1994–2015 Lua.org, PUC-Rio.
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.