My guess is that it means some parts of the library are under GPL, some under LGPL, and some in the public domain. If that's the case, the library as a whole must be considered to be under the GPL, correct?
Yes, that's the case. I just wanted to highlight the fact that parts of it have different licenses.
If the library as a whole must be under GPL license, how is it significant that parts of it were once under LGPL or on the public domain? The purpose of the License field is to tell the user what license the software in the package is under, not to give a history of previous or constituent licensing.
