Not all GIF images have been converted to SVG. So, if you want to use certain images, GIF is still your only choice. So, he may as well make his images available as GIFs.
I think this is a bad plan, because the most-used pieces exist as quality PNG in the alfaeriePNG and alfaeriePNG35 directories, and using GIF files would also use the low-quality images for those. If additional images would have to be added to any directory, it would be better to convert the GIF images for which no SVG version exists to PNG, and add those to the PNG directories. (It should be possible to do that automated in bulk.) These pieces are only very rarely used, and one or two low-quality images don't degrade the experienced quality of a large diagram in a very conspicuous way.
In time the low-quality converted GIFs could be replaced by SVG-derived high-quality PNG, when they are actually used. Diagram-Designer links or Interactive Diagrams using the PNG pieces would then automatically be upgraded to the better quality.
The problem is that there is little incentive to put any effort in creating SVG that is unlikely to be ever used. So use should come first. But when people will be automatically referred to using GIF for their diagrams when they need a rarely used image, no use case for these images as SVG/PNG will ever be created. And if they were, the existing diagrams would not benefit from it.
I think this is a bad plan, because the most-used pieces exist as quality PNG in the alfaeriePNG and alfaeriePNG35 directories, and using GIF files would also use the low-quality images for those. If additional images would have to be added to any directory, it would be better to convert the GIF images for which no SVG version exists to PNG, and add those to the PNG directories. (It should be possible to do that automated in bulk.) These pieces are only very rarely used, and one or two low-quality images don't degrade the experienced quality of a large diagram in a very conspicuous way.
In time the low-quality converted GIFs could be replaced by SVG-derived high-quality PNG, when they are actually used. Diagram-Designer links or Interactive Diagrams using the PNG pieces would then automatically be upgraded to the better quality.
The problem is that there is little incentive to put any effort in creating SVG that is unlikely to be ever used. So use should come first. But when people will be automatically referred to using GIF for their diagrams when they need a rarely used image, no use case for these images as SVG/PNG will ever be created. And if they were, the existing diagrams would not benefit from it.