I'm running Joomla 3.43 and DTRegister 3.12 and seeing this warning as well after a user reaches the thank you page:
Strict Standards: Only variables should be assigned by reference in .../components/com_dtregister/views/message/tmpl/freethanks.php on line 13
It does go away when downgrading the warning level , but wonder if this is of any use in case it points to potential issues. The worry is that warnings like these may affect google ranking.
Nathan is no longer affiliated with DTH since the recent acquisition. You can connect with him and get any type of Joomla website help at
www.JoomlaEmployee.com
.