There are many paid tools like Ethovision, but I am looking for some authentic open source tools (freely available) which can track the movements as well as other significant behaviours in mice.
I am not aware of a "fully integrated" solution (try a google search to prove me wrong!). However, you can certainly build your own based on OpenCV, open3d, torch, and additional python libraries.
You will learn some fantastically useful skills along the way.
A very promising tool has been developed recently by some researchers at the Federal University of Viçosa, Brazil. It seems to be a very promising freely available replacement for Ethovision.