At time of writing, simply increasing the version number on the mod does make it work with 0.18

However, there is some jank with the icons. The icons in 0.18 are apparently 64x64, so the resulting icons are cropped versions of the upper left corner of the normal ones, with the overlay as usual.

The logic relating to generating the icons needs a look, and then GDIW will be ready for 0.18.

I had a look at the logic, and it's not as easy as I thought. They introduced 64x64 icons with 0.18, but not all mods use them. As a result, if GDIW tries to do everything as 64x64 icons, but the mod it's trying to change uses 32x32, it generates an error.
So, it looks like the fix it to iterate through all the icons and find out how big the icon is, and then use either a 64x64 or 32x32 overlay accordingly.
.... or just put up with the issue for now and have some rubbish looking icons which seem to work perfectly well :D

A version 0.18.0 has been uploaded, both to allow 0.18 and 1.0 usage, and also with a fix to Icon Sizes.
Tested with pretty much vanilla, so Im sure glitches will be found in the Icon Size fix.

@Zarnoo : The game will let me combine 64x64 icons with my 32x32 overlays. I will revisit to properly upscale my overlays, but first I have to restore my entire dev environment (yay new computers).