RealGTA3 (=RGTA) is a free add-on for THE BEST GAME OF 2001 - for GRAND THEFT AUTO 3. RGTA is not a product of Rockstar North/Rockstar Games/Take 2 Games! RGTA is the ultimate collection of many GTA3 modifications made by independent authors from all-around the world. The intention of RGTA is to make GTA3 more realistic by adding real cars, buildings or advertisements all over Liberty City. Some information about RGTA development it's in credits section.
Since it is free add-on, you can not profit on RGTA anyhow! Use RGTA at your own risk - I'm not responsible for any hardware or software break-downs or lost data/profit/business/information/wife;-).
If you thought GTA3 was brilliant, then you don't know RGTA:-). RGTA improves GTA3 in many ways - here's a brief list of RGTA features:
New Liberty City