We've released the demo on multiple locations. You can download it from our Moddb page, but also from L4Dmaps: www.l4dmaps.com/details.php?file=22464
You can also subscribe to Final-Salvation to be up to date with the latest public release we bring out: Steamcommunity.com
We sincerely hope that you will enjoy this small sneak-peak and hope that you'll get interested in seeing more of the campaign.
Exi, Aawee & Goudvis