This is not the topic for posting such stuff, but what you have to do is download the previous version of warband(1.143) and install the mod there. No, you don't have to buy the game. Yes, you can have 1.153 and 1.143 at the same time, on the same computer, on the same partition.
Somebody here uploaded a standalone version of the deluge, I tried searching for it just now to link it to you, but I couldn't find it. Look around yourself or download 1.143 and play the deluge.
Hope I helped.
Oh btw, don't be disappointed if you don't see many players online. 1.153 patch fucked up all mods that use warband script extender, deluge being one of them, so for the same reason not many people play.
They will though. They will