mod.io is described as 'open platform for hosting mods created by the team behind ModDB.com and IndieDB.com. It can be integrated in-game using the REST API, C/C++ SDK or engine plugins for Unity, Unreal Engine and GameMaker'. There are six alternatives to mod.io for Online / Web-based, Windows, Linux, Microsoft Azure and Mac. The best alternative is Nexus Mods, which is free. Other great apps like mod.io are Steam Workshop (Free), GameSparks (Free Personal), CrossBrowdy (Free, Open Source) and PlayFab (Freemium).
GameSparks is a Backend-as-a-Service solution provider to mobile game developers to help them reduce the overall cost of development of their games and improve retention of their players and monetization of games post launch.
PlayFab offers a complete backend service to build, launch, and grow live games The backend services your game needs, exposed via our ever-expanding API of more than 200 functions. Use them by themselves, or mix-and-match with your own custom backend services.