I first talked about Tesseract on Phoronix in early 2012 as vastly improving graphics over Cube 2 and at the end of 2012 Tesseract was still running strong and picking up modern engine functionality.
It's been a long time since the last Tesseract update on Phoronix, but I'm happy to report that after thinking about the project and subsequently looking into it a few hours ago, the project is still running strong. The most recent commits to Tesseract's SVN repository is just hours old.
Tesseract recently has picked up features like SDL2 and even Oculus Rift VR support. Tesseract can also create OpenGL 3.0+ Core and OpenGL 2.1 legacy contexts, deferred MSAA/CSS, FXAA, sub-pixel Morphological Anti-Aliasing, and temporal Anti-Aliasing.
Over Sauerbraten, Tesseract also has support for deferred shading, omni-directional point lights, perspective projection spotlight shadowmaps, HDR rendering, real-time diffuse global illumination, and other new and improved graphical features over the aging Cube Engine code-base.
While there isn't a Tesseract release to report on at this time, for those wanting to learn more or to perhaps help out this open-source game engine project, visit their new project site at Tesseract.gg. For graphics geeks, there's also a long article about the Tesseract rendering pipeline.