The following query should identify all assets with OpenVPN installed and last time it was used
SELECT p.upt_hostname AS asset_name, MAX(p.upt_time) AS openvpn_last_accessed
FROM socket_events se
JOIN processes p on se.pid = p.pid
WHERE se.pid > 0 and se.path like '%openvpn%'
GROUP BY p.upt_hostname ORDER BY p.upt_hostname