Good catch, the whole PDF parsing ecosystem is kinda grey on those things. I tried to be extra-careful and I relied on poppler's official statement:

"Note that Poppler is licensed under the GPL, not the LGPL, so programs which call Poppler must be licensed under the GPL as well. See the section History and GPL licensing for more information."

See https://gitlab.freedesktop.org/poppler/poppler/-/blob/master...