Not just an image format, everything you want to become widely adopted and standardized should refrain from using the GPL, even the FSF[1] recommends using the

Not just an image format, everything you want to become widely adopted and standardized should refrain from using the GPL, even the FSF[1] recommends using the Apache License in this specific case. Some libraries implement free standards that are competing against restricted standards, such as Ogg Vorbis (which competes against MP3 audio) and WebM (which competes against MPEG-4 video). For these projects, widespread use of the code is vital for advancing the cause of free software, and does more good than a copyleft on the project's code would do. In these special situations, we recommend the Apache License 2.0. [1] https://www.gnu.org/licenses/license-recommendations.html https://www.gnu.org/licenses/license-recommendations.html