According to Jakarta, "You will need to explicitly reference the external DOCTYPE because of a recent change to call the validating parser"
Of course, you can always copy the files and reference them locally as you are doing.
I don't understand why "it's not a good practice" unless you are afraid of the sun.com server crashing.
You can probably leave out the "external" reference from your DOCTYPE if .dtds are just waaaaaay too inconvenient :roll: but that whole validating parser dealio that Jakarta talks about might be pretty important. I think it would not be a good practice to leave them out of the picture.