Installing a font on a rooted device can result in a boot loop. The app does everything possible to avoid this situation. Before installing a font to your system you should be familiar with ADB and restoring backups in your custom recovery. Always have a nandroid backup before making changes to your system.
If your device is in a boot loop you should reboot into recovery and restore your latest nandroid backup or a flashable ZIP to restore your system fonts. Wiping data will not fix the boot loop.