you can export encrypted script, .gde not .gdc
it's in Export > Script tab.
but in order to do this work properly,
you need to make encrypted template.
get aes256 key here. (try with aes-256-cfb)
and compile template like this.
scons -j 4 platform=x11 target=release
and then, use same key in Export > Script.
now you get encrypted script game.
(IIRC, there was document about this, but I could not find now)