Dynamic Checkbox from Custom Taxonomy

//Adds a filter to form id 3, change number 3 to your form ID.
add_filter("gform_pre_render_3", populate_checkbox);
add_filter("gform_admin_pre_render_3", populate_checkbox);

function populate_checkbox($form){

	//Creating choices and inputs as empty arrays
    $choices = array();
    $inputs = array();

	$categories=  get_categories('taxonomy=services'); // change services to the name of your taxonomy

	$i = 1; // we need a counter to create the field id

        // loop through the array and push the results to the $choices and $inputs arrays
	foreach ($categories as $category) {
                // field_id identify's which element this is going to replace. Change 2 to whatever your field id should be
		$field_id = "2.".$i;

		array_push($choices, array("text" => $category->cat_name, "value" => $category->cat_name));
		array_push($inputs, array("label" => $category->cat_name, "id" => $field_id));

		$i++; // add 1 to the counter for the next loop
	}

    //Adding items to field id 2. Replace 2 with your actual field id. You can get the field id by looking at the input name in the markup.
    foreach($form["fields"] as &$field){
        //replace 2 with your checkbox field id
        if($field["id"] == 2){
            $field["choices"] = $choices;
            $field["inputs"] = $inputs;
        }
    }

    return $form;
}