The addon is mvs (multi vendor shipping) version 1.2.3. The download url is [login to view URL],22. This version is for oscommerece 2.2. Therefore you will need to be able to understand the differences between oscommerece 2.3.1 and 2.2 in order to be able to accomplish this.
Max. bid 30USD . This is easy project if you did it before.