Unfortunately, there isn’t currently a way to subscribe to receive email updates directly from this site.
The good news, however, is that it’s really easy to get email updates by using a “recipe” created in the neat utility IFTTT (If this, then that).
Have a look at: https://ifttt.com/recipes/147561-rss-feed-to-email
You’ll need to register with IFTTT, and provide an email address for notifications about new events to be sent to.
The “feed url” to specify is: http://opendata-aha.net/events/feed/