Clicking the Download link (https://www.dropbox.com/s/us5qwxxmuiia56y/ImSVG_Open.FileTypev0.18.zip?dl=0) displays the contents of the Zip file in Dropbox.
If there is a direct way to download the files from there it isn't apparent when have chosen not to log into DropBox (despite the comment saying "Click the Download button", there isn't one).
You can, however, just go up to the URL, change dl=0 to dl=1 and the zip file will download when you press Enter (the URL will also revert to dl=0).