WP Job Manager Field Editor add max selections support for Taxonomy Checklist field (only required for 1.7.5 or older, 1.7.6+ has this already integrated) MAKE SURE YOU READ ALL COMMENTS

integration.php

<?php
// THIS IS JUST A SMALL UPDATE YOU NEED TO MAKE IN A FILE:
// JUST READ COMMENTS BELOW AND MAKE MINOR UPDATE YOURSELF

// EDIT THE FILE LOCATED AT /wp-content/plugins/wp-job-manager-field-editor/classes/integration.php 
// and on LINE 328 inside the 'locate_template' function you will find this block of code:

switch ( $template_name ) {
		case 'form-fields/term-checklist-field.php':
			wp_enqueue_script( 'jmfe-term-checklist-field' );
			break;
		default:
			if ( file_exists( WPJM_FIELD_EDITOR_PLUGIN_DIR . '/templates/' . $template_name ) ) {
				/**
				 * Support customized theme template overrides
				 *
				 * Theme template structure should match /templates/THEMENAME/
				 */
				$theme_name = self::get_theme_name( TRUE, FALSE );
				if ( is_string( $theme_name ) && ! empty( $theme_name ) && file_exists( WPJM_FIELD_EDITOR_PLUGIN_DIR . "/templates/{$theme_name}/" . $template_name ) ) {
					$template = WPJM_FIELD_EDITOR_PLUGIN_DIR . "/templates/{$theme_name}/" . $template_name;
				} else {
					$template = WPJM_FIELD_EDITOR_PLUGIN_DIR . '/templates/' . $template_name;
				}
			}
			break;
	}

// ONCE YOU FIND THAT BLOCK OF CODE ABOVE (THE ORIGINAL BLOCK OF CODE)
// UPDATE THAT BLOCK OF CODE TO MATCH THIS BLOCK OF CODE BELOW:

switch ( $template_name ) {

	// Allow for adding custom switch later on if needed, right now only default
	default:

		if( $template_name === 'form-fields/term-checklist-field.php' ){
			wp_enqueue_script( 'jmfe-term-checklist-field' );
		}

		if ( file_exists( WPJM_FIELD_EDITOR_PLUGIN_DIR . '/templates/' . $template_name ) ) {

			/**
			 * Support customized theme template overrides
			 *
			 * Theme template structure should match /templates/THEMENAME/
			 */
			$theme_name = self::get_theme_name( TRUE, FALSE );
			if ( is_string( $theme_name ) && ! empty( $theme_name ) && file_exists( WPJM_FIELD_EDITOR_PLUGIN_DIR . "/templates/{$theme_name}/" . $template_name ) ) {
				$template = WPJM_FIELD_EDITOR_PLUGIN_DIR . "/templates/{$theme_name}/" . $template_name;
			} else {
				$template = WPJM_FIELD_EDITOR_PLUGIN_DIR . '/templates/' . $template_name;
			}
		}

		break;
}

js.php

<?php

// THIS IS JUST A SMALL UPDATE YOU NEED TO MAKE IN A FILE (DO NOT COPY ENTIRE CONTENTS OF THIS BLOCK LIKE OTHERS):
// JUST READ COMMENTS BELOW AND MAKE MINOR UPDATE YOURSELF

// EDIT THE FILE LOCATED AT /wp-content/plugins/wp-job-manager-field-editor/classes/admin/js.php 
// and on LINE 611 find this block of code:

"term-checklist"   => array(
  "show"     => array('taxonomy', 'default'),
  "hide"     => array('placeholder'),
  "required" => array('taxonomy')
),

// UPDATE THAT FILE ADDING THE 'max_selected' field to show, the block of code should look like this after the update:

"term-checklist"   => array(
  "show"     => array('taxonomy', 'default', 'max_selected'),
  "hide"     => array('placeholder'),
  "required" => array('taxonomy')
),

term-checklist-field.php

<?php

// COPY THE ENTIRE CONTENTS OF THIS CODE BLOCK/FILE TO:
// wp-content/plugins/wp-job-manager-field-editor/templates/term-checklist-field.php

// YOU MUST CREATE A NEW FILE WITH THE EXACT FILENAME OF 'term-checklist-field.php' AND PLACE IT INSIDE
// wp-content/plugins/wp-job-manager-field-editor/templates/ DIRECTORY

/**
 * Shows `checkbox` form fields in a list from a list on job listing forms.
 *
 * This template can be overridden by copying it to yourtheme/job_manager/form-fields/term-checklist-field.php.
 *
 * @see         https://wpjobmanager.com/document/template-overrides/
 * @author      Automattic/Myles McNamara
 * @package     WP Job Manager Field Editor
 * @category    Template
 * @version     @@version
 */

if ( ! defined( 'ABSPATH' ) ) {
	exit; // Exit if accessed directly
}

// Default should be empty string, only when max selected is defined should it have a custom string
$max_selected_class = '';

// Check for custom configurations (that require separate jQuery initalization)
if ( array_key_exists( 'max_selected', $field ) && ! empty( $field['max_selected'] ) ) {

	$max_selected = $field['max_selected'];
	$esc_key      = esc_attr( $key );
	// Set to specific class to allow max selected jQuery handling
	$max_selected_class = 'jmfe-term-checklist-max-checked';
}

?>
<ul class="job-manager-term-checklist job-manager-term-checklist-<?php echo $key; ?> <?php echo $max_selected_class; ?>" data-meta-key="<?php echo $esc_key ?>" data-max-selected="<?php echo $max_selected; ?>">
<?php

	require_once( ABSPATH . '/wp-admin/includes/template.php' );

	if ( empty( $field['default'] ) ) {
		$field['default'] = '';
	}

	$args = array(
		'descendants_and_self'  => 0,
		'selected_cats'         => isset( $field['value'] ) ? $field['value'] : ( is_array( $field['default'] ) ? $field['default'] : array( $field['default'] ) ),
		'popular_cats'          => false,
		'taxonomy'              => $field['taxonomy'],
		'checked_ontop'         => false
	);

	// Max selections handling for args
	if( isset( $max_selected ) && ! empty( $max_selected ) ){

		// If value has more than allowed selected, set selected_cats to max amount of values
		if ( is_array( $args['selected_cats'] ) && ! empty( $args['selected_cats'] ) ) {
			$args['selected_cats'] = array_slice( $args['selected_cats'], 0, $max_selected );
		}

		// Set description showing max selections (if custom one not specified)
		if ( empty( $field['description'] ) ) {
			$field['description'] = sprintf( __( 'Maximum selections: %s' ), $max_selected );
		}

	}

	// $field['post_id'] needs to be passed via the args so we can get the existing terms
	ob_start();
	wp_terms_checklist( 0, $args );
	$checklist = ob_get_clean();
	echo str_replace( "disabled='disabled'", '', $checklist );
?>
</ul>
<?php if ( ! empty( $field['description'] ) ) : ?><small class="description"><?php echo $field['description']; ?></small><?php endif; ?>

term-checklist.min.js

// UPDATE THE EXISTING FILE term-checklist.min.js LOCATED AT
// wp-content/plugins/wp-job-manager-field-editor/assets/js/term-checklist.min.js
// WITH THE ENTIRE CONTENTS OF THIS CODE BLOCK/FILE

jQuery( function ( $ ) {

	$( '.job-manager-term-checklist input' ).prop( 'disabled', false );

	$( '.jmfe-term-checklist-max-checked' ).each( function ( index ) {

		var meta_key = $( this ).data( 'meta-key' );
		var max_selected = $( this ).data( 'max-selected' );

		if ( meta_key && max_selected ) {

			window[ meta_key + '_checked' ] = [];

			window[ '$' + meta_key + '_check' ] = $( '.job-manager-term-checklist-' + meta_key + ' input[type=checkbox]' ).change( function () {

				if ( this.value == - 1 && this.checked ) {
					window[ '$' + meta_key + '_check' ].not( this ).prop( 'disabled', true ).prop( 'checked', false );
					window[ meta_key + '_checked' ] = [];
				} else {
					window[ '$' + meta_key + '_check' ].prop( 'disabled', false );
					window[ meta_key + '_checked' ].push( this );
					window[ meta_key + '_checked' ] = $( window[ meta_key + '_checked' ] );
					window[ meta_key + '_checked' ].prop( 'checked', false ).slice( - max_selected ).prop( 'checked', true );
				}
			} );

		}

	} );

} );

Most of the updates are just small code changes in file, the ONLY file you need to create is the term-checklist-field.php all others should already exist.

The only file that will be updated with everything in the code block, is the term-checklist-min.js file ... all other files/updates are minor code block changes, read comments for all details