Yes you do need curing salt to make jerky that is safe.
You can get by without using curing salt to make your jerky and it will usually cure just fine.
However to make safe jerky you should use curing salt when making the jerky because not only does the curing salt help the jerky cure the curing salt also helps keep bacteria off of the jerky while it's curing.
If you don't use curing salt on the jerky when you make it then bacteria can form on the jerky which can make you sick.
So to prevent bacteria from forming on the Jerky make sure you use curing salt.
Curing salt also makes the jerky much better to eat and helps the jerky cure faster as well.