PHP fatal error on plugin activation under non-direct filesystems

[cssjoe]

When activating boldgrid-inspirations as the only active plugin:

Oct  9 16:02:09 host php-cgi: PHP Fatal error:  Uncaught Error: Class 'Boldgrid\Library\Library\License' not found in /home/user/public_html/wp-content/plugins/boldgrid-inspirations/vendor/boldgrid/boldgrid-inspirations-premium/src/Premium/Attribution.php:39
Stack trace:
#0 /home/user/public_html/wp-content/plugins/boldgrid-inspirations/boldgrid-inspirations.php(65): Boldgrid\Inspirations\Premium\Attribution->__construct()
#1 /home/user/public_html/wp-admin/includes/plugin.php(2141): include('/home/user/publ...')
#2 /home/user/public_html/wp-admin/plugins.php(175): plugin_sandbox_scrape('boldgrid-inspir...')
#3 {main}
  thrown in /home/user/public_html/wp-content/plugins/boldgrid-inspirations/vendor/boldgrid/boldgrid-inspirations-premium/src/Premium/Attribution.php on line 39

I get that fatal when using any non-direct filesystems: ssh2, ftpext, ftpsockets

Replicate using define('FS_METHOD', 'ftpext'); in wp-config.php.