Any good freedom hardware for game development?

I don't know the answer, but note that using software is always a possibility if the GPU doesn't support the version of OpenGL you need. I believe most distros are set up to run any unsupported OpenGL calls in software, so you should be good regardless.

Also, there are some 2-D libraries and engines that run entirely in software, so with those you won't have any problem. In fact 2-D games don't benefit all that much from hardware acceleration these days. My SGE Game Engine is an example of a software-rendered engine. Probably not entirely relevant since I suppose whatever class you're taking will probably involve 3-D, but just mentioning that for completeness.

You have same trouble as me. I am student, I also do Android Studio and Unity. I love Unity, nut yes, is proprietary. I don't know how good is Godot, but I think that is the best alternative possible to Unity.

I have T400 but did not tested, greatest laptop you can buy but shittiest screen ever, it is almost painful to see at it, colors are fully washed out. And I have T400 led and ccfl versions.

I think that T400 can be enough for game developement, 8gb of ddr3 ram are great, but old core2duo, if you buy T400, take T9600, this one costs about 20€.

What you have to find out is, which GPU is on your Lenovo T400. AFAIR it is the 4500MHD. Please find out the exact name, I'm not sure which one it is. Now, look into which OpenGL version that specific GPU supports.

I believe the 4500MHD supports OpenGL 2.0 and nothing above, but don't quote me on that. Support for newer OpenGL versions may appear in future releases of linux-libre, since that GPU is letting doing most of the work in software anyway.

Now that you know which OpenGL version your GPU supports, you can ask the Gobot developers, if you can use their engine with the highest OpenGL version your GPU can support, or if using the Godot engine requires a higher version of OpenGL at the very least.

Personally, I don't expect there to be any problems at all. You can't DISPLAY sophisticated 3D graphics on an integrated Intel GPU. But using a specific engine to develop a game should not be a problem. The Godot Engine can even be used for 2D games, so at the very least this should be possible.

Edit: when you go to the downloads page of the Godo Engine website, it says: "OpenGL ES 3.0 compatible hardware" is required for version 3.0 of the engine. But there is an archive of older versions too, so you should be able to do something with the Godot Engine even if your GPU does not support OpenGL ES 3.0.