To update the Fedora mingw-freeimage package I'd need mingw-libwebp to also build libwebpmux and libwebpdemux. I've prepared the update here  (updating to the lastest upstream release while at it). I had already requested commit ACLs to mingw-libwebp some time back when I requested an update from an old version, which Kalev Lember eventually took care of. If you are no longer interested in the package, I'd appreciate if you could grant me acls and I'll be happy to do the upgrade myself - I already maintain the native libwebp package.
Per non responsive maintainer policy: ping?
I'm co-maintainer on this package. Please apply for access
through https://admin.fedoraproject.org/pkgdb and I will grant
it for you.
Thanks. Actually I requested access some time ago, these are still pending in pkgdb.
It looks like I'm not permitted to approve those ACLs, so you
will have to contact the maintainer after all.
mingw-libwebp-0.4.3-1.fc23 has been submitted as an update to Fedora 23. https://bodhi.fedoraproject.org/updates/FEDORA-2015-bd7d490fde
mingw-libwebp-0.4.3-1.fc23 has been pushed to the Fedora 23 testing repository. If problems still persist, please make note of it in this bug report.
If you want to test the update, you can install it with
$ su -c 'dnf --enablerepo=updates-testing update mingw-libwebp'
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2015-bd7d490fde
mingw-libwebp-0.4.3-1.fc23 has been pushed to the Fedora 23 stable repository. If problems still persist, please make note of it in this bug report.