Hey, try to search on hbgames.org on submitted RGSS script.
Search there, here's the keyword = letter by letter
Download the demo
Open the script on the demo
Copy it
And remove these lines
#------------------------------------------------------------------------------
# SDK log
#------------------------------------------------------------------------------
SDK.log('Letter by Letter Message Window', 'Slipknot', '1.1', '16.08.06')
#------------------------------------------------------------------------------
# Begin SDK Enabled Check
#------------------------------------------------------------------------------
if SDK.state('Letter by Letter Message Window')
and this line on the last part of the script
#------------------------------------------------------------------------------
# End SDK Enabled Test
#------------------------------------------------------------------------------
end