edd.php

<?php

/**
 * Disable commission on an entire product category in Easy Digital Downloads
*/
function affwp_custom_wc_disable_commission_per_category( $referral_amount, $affiliate_id, $amount, $reference, $product_id ) {
 	
 	// Array of categories to disable commission for. Separate by a comma and use either the term name, term_id, or slug 
	$disabled_categories = array( 'category-one', 5 );

	// Disable commission if product exists in array of categories
	if ( has_term( $disabled_categories, 'download_category', $product_id ) ) {
		$referral_amount = 0.00;
	}

    return $referral_amount;
}
add_filter( 'affwp_calc_referral_amount', 'affwp_custom_wc_disable_commission_per_category', 10, 5 );

woocommerce.php

<?php

/**
 * Disable commission on an entire product category in WooCommerce
*/
function affwp_custom_wc_disable_commission_per_category( $referral_amount, $affiliate_id, $amount, $reference, $product_id ) {
 	
 	// Array of categories to disable commission for. Separate by a comma and use either the term name, term_id, or slug 
	$disabled_categories = array( 'category-one', 5 );

	// Disable commission if product exists in array of categories
	if ( has_term( $disabled_categories, 'product_cat', $product_id ) ) {
		$referral_amount = 0.00;
	}

    return $referral_amount;
}
add_filter( 'affwp_calc_referral_amount', 'affwp_custom_wc_disable_commission_per_category', 10, 5 );