I've just submitted v2.1.5 of One-Page Checkout to the Zen Cart moderators for review and will post back here when it's available for download.

This release contains changes associated with the following GitHub issues:

#213: Use 'TEXT_OPTION_DIVIDER' when displaying the shopping-cart.
#214: Correct 'zen_get_tax_locations' override when guest's billing=shipping.
#215: Use 'zen_is_logged' in when checking customer login status on the checkout_one_confirmation page.
#216: Enable integration with Gateway Processing Services (gps) payment method.