Okam Studio has recently released a new version of Godot, an open source and multi-platform game engine that aims to provide developers with a development platform like Unity3D.
Godot offers an excellent graphical user interface that allows developers useful tools for the design of new 2D and 3D game, including various animations, scripting, physics and debugging tools, in addition to supporting a lot of VCS for team working.
Godot can also expand functionality through third-party plugins, and also has the support for exporting to any type of platform.
Godot provides a huge set of common tools, so you can just focus on making your game without reinventing the wheel. Godot is completely free and open source under the very permissive MIT license. No strings attached, no royalties, nothing. Your game is yours, down to the last line of engine code.