mypmro-change-username-text.php

<?php
/**
 * This recipe will change the default Username text to Ham Radio Callsign
 *
 * You can add this recipe to your site by creating a custom plugin
 * or using the Code Snippets plugin available for free in the WordPress repository.
 * Read this companion article for step-by-step directions on either method.
 * https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */
 

function mypmpro_change_username_text( $translated, $text, $domain ){

	if( $text == 'Username or Email Address' || $text == 'Username' ){
		$text = 'Ham Radio Callsign';
	}
	return $text;
}
add_filter( 'gettext', 'mypmpro_change_username_text', 10, 3 );