If you inslall the official 4.3 or 4.4 OTA it will come with knox. The only way around it is to flash a custom rooted rom either 4.3 or 4.4.
OR you can take the 4.3 OTA then the 4.4 OTA then root and manually remove the knox files with Root Explorer etc. You can take the OTA's but what's the point in doing that if you want to have root and no knox? Just flash a custom rooted no knox 4.4 ROM. Much easier.