I don't know of anything as straight forward as python offers either, but here are two options that get the job done:
Consider a file called included.jsl:
a = function({}, 1);
b = function({}, 2);
To load the function directly in the context of your script:
names default to here(1);
//load the new file in a local here namespace
Eval( Eval Expr( local here(
include("included.jsl");
//Reference the original script's here namespace in this local here namespace
//Eval, Eval Expr, and Expr cause the namespace("here") to be evaluated
//outside of this 'local here' context.
ns = Expr( namespace("here") );
//copy and functions you want to keep
ns:a = here:a;
) ) );
//Now functions are in this namespace
a();
Or, to keep the function in a separate namespace:
names default to here(1);
//create namespace to hold functions you want to keep from included file
ns = new namespace();
//load the new file in a local here namespace
Eval( Eval Expr( local here(
include("included.jsl");
//Reference the ns namespace in this new here namespace
ns = Expr( ns );
//pick and choose any functions you want to keep
ns:a = here:a
) ) );
//Now either call the functions from the ns namespace
ns:a();
//or copy them to the here namespace
a = ns:a;
a();