Greatest mod ever, yes.
However, even though the ESF team doesn't get paid, it must be nice to know that thousands of people are playing their game and many have chosen not even to go HL2 simply because this mod is forever staying on HL1. I know if I were a member of the ESF Team, I'd be waking up feeling good about what I've done every morning. Turning thousands of strangers into a tight community, it truly is a wonder. Making a quality game that rivals many other paid games for replay value is also a kudos to the team.
Immortalized for the rest of HL1's existance, ESF will go down as one of the top mods ever. In my experience, ESF has outlasted some of the finest console and computer games I've ever played. Most of the games I have played don't last more than a few months. ESF has gone years for me. Thats just amazing-- and I doubt I'm the only one.