LuaZip is free software (MIT license): it can be used for both academic and commercial purposes at absolutely no cost. There are no royalties or GNU-like "copyleft" restrictions. LuaZip qualifies as Open Source software. Its license are compatible with GPL. LuaZip is not in the public domain and the Kepler Project keep its copyright. The legal details are below.
The spirit of the license is that you are free to use LuaZip for any purpose at no cost without having to ask us. The only requirement is that if you do use LuaZip, then you should give us credit by including the appropriate copyright notice somewhere in your product or its documentation.
The LuaZip library was designed and implemented by Danilo Tuler. It is maintained by Peter Melnichenko. Part of the code is a derived work from the Lua standard I/O library, copyrighted by Tecgraf, PUC-Rio.
Copyright © 2003-2007 The Kepler Project. Copyright © 2016-2017 Peter Melnichenko
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.