Final Draft 10 and Final Draft 9.1 are compatible with Sierra. The FD10 installer is HERE; the FD9.1 installer is HERE.
Final Draft 8 is not recommended for Sierra and will not be updated. More information is here:
Final Draft 7 / 6 / 5 are not compatible with Sierra.
If you own Final Draft 7 / 6 / 5 and you want to run Final Draft on a Sierra computer, you will need to upgrade to FD10. This upgrade is not free. Click HERE for more information on purchasing the FD10 upgrade.