I don't like the less serious licenses because they often don't explicitly declare that your software is distributed with no warranty.
This makes you liable to be sued in certain jurisdictions, where simply distributing software is assumed to also provide support, or you could be held responsible for damage it causes or misuse.
Of course, the chance of someone suing you is extremely slim. And courts are ran by humans, who can interpret the spirit of the law, rather than the letter, so I would hope they would be gracious and understanding of the open source model. But it's better to just not take chances.
~~It looks like these tags are stored in filesystem xattrs themself, not in dolphin or kde metadata. That is, even if you load up gnome's file browser, or another file browser, it should still be able to read them.~~
Nope, it looks like the tags used are KDE specific, even though any software could theoretically implement support for reading and writing them.
https://wiki.archlinux.org/title/Extended_attributes
https://www.freedesktop.org/wiki/CommonExtendedAttributes/