In the past, Codemasters had a protected file in the games coding, which would protect against tampering of things like lap times, and any forms of cheating. If the players modified this file in anyway, it would not allow them access to the online play, would not allow them to save, and disable all forms of achievements. They have also noted that some people modding the file also had no malicious intent whatsoever, and so a solution was brewed up to this. Codemasters have taken steps to allow the modding community to play games with mods installed, though the mods will be saved to a completely different save file, leaving your unmodified saves the same.
You won’t be able to access their online service, RaceNet, online play, leaderboards, and achievements will be disabled in this modified save data, in order to preserve the integrity of the main game. A link to the post with all information can be found here.
For me, it’s nice to see that game developers are taking steps to help the modding community with their games. Games like these would benefit from some modders that can change some things for fun, making new gametypes, new maps,/tracks for people to play on, new cars with crazy designs. The possibilities of this are endless with modders working to make the game more fun that what is already is. I wish Codemasters the best of luck with this decision, and hope that it will allow full mod support one day for online play.
This is Travis, singing off.