@iska That is not free software.

There is a modified version of MIT expat dumped in the root, but there is no indication as to which files that license applies to.

There is also a thirdparty/LICENSE.darts_clone.txt file, but that is only a template and doesn't apply to anything as the organization hasn't been filled.

thirdparty/zip.c & thirdparty/zip.h are proprietary software as there is intentionally no license and only a warranty disclaimer;
/*
* 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 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.
*/


As always, such tools turn out to be proprietary.