I can't tell what license is applicable.

On https://labplot.org/frequently-asked-questions/ , under "Under what license is LabPlot released?", it says this:

> LabPlot is licensed under GNU General Public License, version 2.0 or later, so to put it in a few sentences:

> You are free to use LabPlot, for any purpose

> You are free to distribute LabPlot

> You can study how LabPlot works and change it

> You can distribute changed versions of LabPlot

> In the last case you have the obligation to also publish the changed source code as GPL.