Well, if we rely on web info only, last version date is 2012-04-24 :
http://www.ararat.cz/synapse/doku.php/startLatest change on svn from 2018-08-22 is about cosmetic, AFAIK. Few serious chages happened around 2017-06-07 when OpenSSL 1.1.0 is added and some error was fixed.
But in average, few changes in a year can be hardly called "maintenance", since code is still extremely chaotic.
In the past, I did used synapse quite a bit, while I still did not make any server app. But since code was disasterous and many usefull functionlity missed, I have contacted Gebauer several times with code updates and new usefull methods ICS and Indy had and I used it quite a bit, but he refused to do anything about...
Then I stopped to participate and started to maintained it myself for my own purposes only. Then I swithched to Piere's ICS completely after extensive code inspection and provided many tests - I was extremely satisfied with, including making server apps. I'm talking about time 15 years ago or so.