We’ve found out that there were several problems with the prebuilt libraries that we ship with Fuse when it comes to compatibility with older Mac models.
I’ve submitted a pull request for a fix, and you can follow its progress here. It’s too late for it to be included in the coming patch release since that’s already being tested, but it will likely be included in the release after that. If you’re feeling brave you can try a local checkout of the fuselibs branch in the pull request linked above in the meantime.
The Fuse 1.0.1 pre-release, available at https://www.fusetools.com/downloads/channel/qa, now allows you to pass defines to the preview command again, so another workaround for this issue that should work is to start Fuse with fuse preview . -DDISABLE_HARFBUZZ. The fix mentioned above will be included in the release after 1.0.1 if all goes according to plan.