> I pasted my expressions script below. It looks like it calculated d1 and d2 correctly.
Yes, that looks correct.
> Is it possible that one should interpret traditionally-calculated IAT D scores (as they are calculated within the Inquisit script)
> differently than BIAT D scores calculated via the SPSS syntax?
No. There is no difference. At least in theory / leaving aside the sign mismatch under discussion, the script performs the exact same calculations as the SPSS syntax.
It's perfectly possible that the wrong order of terms is in the SPSS syntax, not the script.