The library is not unusable with this license. Anyone writing GPLv3 software to begin with would be just fine with using this license. The question you have t

The library is not unusable with this license. Anyone writing GPLv3 software to begin with would be just fine with using this license. The question you have to ask yourself is: am I OK with releasing my software under the GPLv3, or am I OK with rewriting this library if I decide to relicense my software under some other license. If you're OK with that, then you can use this library.