GTA 3 and Vice City's source code has been reverse-engineered, allowing for unofficial ports to new consoles.
According to the project on Github, the game has already been ported to Nintendo Switch, PS Vita, and the Wii U. More importantly, this also means that modders will be able to work their magical ways on the game, implementing things like ray-tracing; much like that Super Mario PC port.
While the main interest of reverse-engineering a game's source code is to try and port it to other consoles, this doesn't seem to be the only reason for these GTA games simply because the game has been made available on plenty of different systems.
As we mentioned above, the modding part is what's going to be really interesting. Having access to the source code will allow modders to basically add completely new scenarios and features to the games, as well as being able to update the graphics for modern systems, alongside making unofficial ports to consoles like the Switch and the PS Vita.
You can see the team's work on Github, where they explain their progress and the plans they have for using the game's source code.
It begins: "In this repository, you'll find the fully reversed source code for GTA III (master branch) and GTA VC (Miami branch)", and continues to explain "the project has also been ported to the Nintendo Switch, Playstation Vita, and Nintendo Wii U".
The Github page also goes on to mention that the team has made a bunch of 'improvements' to the games by "implementing changes" to the original. These range from small bug fixes to debugging menus to widescreen support and removing loading screens between islands.
At the very bottom of the page, the team behind this project has clarified that "the code should only be used for educational, documentation and modding purposes.
We do not encourage piracy or commercial use. Please keep derivate work open source and give proper credit".
Related Forum: Grand Theft Auto Forum