sunbelt's firewall is in two flavors like ewido
and like ewido the free is forever but the download is the $ version for a short period of time
some of the $ would be nice to have but you can live without

and is close to ZA as the free vs the $ version
this is from their page
http://www.sunbelt-software.com/Kerio.cfmthe major differences
Product: SKPF 4 - free SKPF 4 - full
NETWORK SECURITY
Packet filter YES YES
File integrity control YES YES
Application communication control YES YES
Application launch control YES YES
Network Intrusion Prevention System YES YES
Host-based Intrusion Prevention System NO YES
CONTENT FILTERING
Advanced Identity Theft Protection NO YES
Script blocking (JavaScript, VB script) NO YES
Referrer and Cookies blocking NO YES
Ad blocking NO YES
Pop-up windows blocking NO YES
STATISTICS, LOGGING
Statistics of attacks and blocked ads YES YES
Automatic update checker YES YES
Extended logging YES YES
Syslog NO YES
Runs as Internet Gateway NO YES