TiddlyWiki is published under a permissive BSD 3-Clause License stored in the shadow tiddler $:/core/copyright.txt:
TiddlyWiki created by Jeremy Ruston, (jeremy [at] jermolene [dot] com)
Copyright (c) 2004-2007, Jeremy Ruston
Copyright (c) 2007-2024, UnaMesa Association
All rights reserved.
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
* Redistributions of source code must retain the above copyright notice, this
list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright notice,
this list of conditions and the following disclaimer in the documentation
and/or other materials provided with the distribution.
* Neither the name of the copyright holder nor the names of its
contributors may be used to endorse or promote products derived from
this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 'AS IS'
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.In layman's terms, the license says that you can take TiddlyWiki and do anything you want with it without any license fee payment or other legal obligation to the creators of TiddlyWiki or anyone else. The quid pro quo is that there is no warranty or guarantee with open source projects like TiddlyWiki. You can't sue the contributors to TiddlyWiki for any loss or damage due to the use of TiddlyWiki: even if your data is lost due to a tragic chain of circumstances that involves TiddlyWiki.
You are respectfully requested that to make an attribution to the project, but there's no obligation to do so.
For the avoidance of doubt, any information that you choose to store within your own copy of TiddlyWiki remains yours; using TiddlyWiki to publish content doesn't change whatever rights you may have to that content.