Yep! Though depending on various production factors it may not stay up forever. Progress from the Steam demo will carry over to the full game, though! There are exactly three places to play the official demo:

• Play the "How Many Dudes?" PC demo on Steam. This is the best way to try out How Many Dudes: it's at full 4K resolution and has the best performance!
• Play the "How Many Dudes?" web demo on itch.io
• Play the "How Many Dudes?" web demo on Gx.games. This is the same as the itch.io version.

Any other demo or "free" version you find is not official, and is probably a scammer trying to put malware on your devices. Stay safe out there!