#Bash/GolfScript, 72 bytes, score 2<sup>6</sup>/72 = 8/9 (~0.888...)

    .~0 () 
    { 
        declare "-f" @* ".~0" " ()
     "+@n.;
        echo '.~0;'
    }
    .~0;

Contains a single trailing space on the first two lines.

[Try it online in Bash.](https://tio.run/##S0oszvj/X6/OQEFDU4GrWoFLAQhSUpNzEotSFZR005QUHLQUlIDySgpKQCVcCkraDnl61mBlqckZ@QrqQDlrda5aLhD9/z8A)  
[Try it online in GolfScript.](https://tio.run/##S8/PSStOLsosKPn/X6/OQEFDU4GrWoFLAQhSUpNzEotSFZR005QUHLQUlIDySgpKQCVcCkraDnl61mBlqckZ@QrqQDlrda5aLhD9/z8A)

Simply modification of [_@jimmy23013_'s answer for the "_Write a Polyquine_" challenge](https://codegolf.stackexchange.com/a/37857/52210). The modification that was done was removing the trailing space after the third line, and changing `\n"+@n.;` to `\n "+@n;`.

Bash will print lines 1 and 2 like this:

    .~0 ()    <- Trailing space
    {         <- Trailing space

And GolfScript will print lines 1 and 2 like this:

    .~0 ()   <- No trailing space
     {       <- Both leading and trailing space

Here the base program, Bash output, and GolfScript outputs respectively with the new-lines replaced with `\n`:

    .~0 () \n{ \n    declare "-f" @* ".~0" " ()\n "+@n.;\n    echo '.~0;'\n}\n.~0;
    .~0 () \n{ \n    declare "-f" @* ".~0" " ()\n "+@n.;\n    echo '.~0;'\n}\n.~0;
    .~0 ()\n { \n    declare "-f" @* ".~0" " ()\n "+@n.;\n    echo '.~0;'\n}\n.~0;

          ^^^ Note the difference here