Quote Originally Posted by lat9 View Post
FWIW, I was able to correct the integration issue by editing the /includes/modules/pages/checkout_payment/jscript_square.php (it's also copied to the /checkout_one/jscript_square.php for the OPC integration) and changing:
Code:
if ($payment_modules->in_special_checkout()) {
    return false;
}
to
Code:
if ($payment_modules->in_special_checkout() || (isset($payment_modules->paymentClass) && $payment_modules->paymentClass->code != 'square')) {
    return false;
}
The result is that Square's jQuery module doesn't load if the payment class is selected and it's not Square.
Please note, after additional thought, that's not going to work! The change needs to be made to the jQuery processing itself; otherwise, the payment method can't be changed to Square after a previous selection of a payment method.

Back to the drawing board ...