[brianwawok]

I think license depends on your goal. If your goal is to create a web image format.. you need all the browsers to agree to include you. All browsers will not add a GPLv3 image type. Therefore it is dead before it launched.

[davexunit]

The author has expressed interest in dual-licensing, so there will probably still be options. GPLv3+ or LGPLv3+ sounds reasonable.

[snuxoll]

LGPLv3 will still prevent use of Windows Phone, iOS and Android.

[davexunit]

No, that's backwards. Microsoft and Apple and Google prevent the usage of the GPL/LGPL. Don't blame the GPL for the bad behavior of large corporations that are using their immense power to try to stop copyleft.