What version of Devpac are you using AlfaRomeo...?
I put this code into Devpac V3.18 and it assembled and ran with no problems.
By the way, code would be shorter like this:
Code:
lea TEXT(pc),a0
move.b (a0)+,d0
subq.b #1,d0
lea COPY(pc),a1
loop move.b (a0)+,(a1)+
dbf d0,loop
move.b #0,(a1)
rts
TEXT dc.b 5,"HELLO"
COPY ds.b 6
EDIT: Only just noticed that Bipps had already posted a shortened version earlier... ;-)