Consider using PIL in conjunction with pillow-heif:
pip3 install pillow-heif
from PIL import Image
from pillow_heif import register_heif_opener
register_heif_opener()
image = Image.open('image.heic')
That said, I’m not aware of any licensing/patent issues that would prevent HEIF support in Pillow (see this or this). libheif is widely adopted and free to use, provided you do not bundle the HEIF decoder with a device and fulfill the requirements of the LGPLv3 license.