Lafayette Limo and Reindeer Shuttle are definitely the most popular options. I have not heard of any free service being operated by Purdue.
That said, there is a lot of ride sharing going on. A ton of students live in the Indy and Chicago areas and it’s usually pretty easy for people to find rides.
This was started by a group of Purdue students:
The parent FB group also facilitates ride sharing all the time.