Splunk Enterprise Trial version works for 60 days and then you have to migrate to Free license (see above) or buy Enterprise license (it is very expensive if you want to have it on small sites like my imagepush.to). The solution I found is to reinstall it every 2 months:
# remove splunk, if you have it installed already
sudo rpm -e splunk
# Splunk for Amazon Linux (32bit)
curl -O http://126.96.36.199/releases/4.3.2/splunk/linux/splunk-4.3.2-123586.i386.rpm
sudo rpm -U splunk-4.3.2-123586.i386.rpm
sudo /opt/splunk/bin/splunk start
Then login to splunk web and set password. All settings will be in place already.