There isn't a WT-Mod. The WT is integrated into the base game and is written into the base code in every release since the first one.
What
RiamMar's mod does is two things:
* Decisions mod: It allows you to change IMPORTANT choices you took previously (paths with the girls, in what chance you open their route, etc.). It's integrated into the game and up to date (because RiamMar is a dear and he works hard to have it ready before release) and doesn't need a separate download.
* Family mod: It substitutes the official incest patch and allows you to change the incest/non-incest mode dynamically. If you install the official incest patch, you don't need it if you won't play the non-incest version. If you play the non-incest version, you don't need to download it or the official incest patch. It's only necessary if you want to switch from incest/non-incest.