Barebones CMS is released under a dual-license. For those who want the licenses and restrictions in English (i.e. not legaleze), here's a brief summary:
While the product itself is free, financial donations are highly encouraged - especially if you start asking questions on the support forums. This is a professional product - you would want money for your time spent as well. If you can't donate financially, that's fine but consider spreading the word among your friends and work associates.
A lot of CMS products require attribution (e.g. "Powered by Barebones CMS"). While the gesture would be nice even for Barebones CMS, it paints a big target on your website for hackers looking for outdated, vulnerable versions of a product. For many open source products, all a hacker generally has to do is go to Google and search for "Powered by [product name]" and they get a list of potentially vulnerable websites.
The only requirement for Barebones CMS is that all copyrights remain intact within the code itself, which shouldn't be a problem for anyone because the copyright lines are never publicly displayed.
The MIT License
Copyright (c) 2013 CubicleSoft
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.
Copyright (C) 2013 CubicleSoft
This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version.
This software is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License along with this software; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA