I guest its the most recent "old UI" (i.e. pre 2.5) of blender. 2.49 : https://forum.unity.com/attachments/800px-blender_2-49b_init... Version 2.5 : https://2.bp.blogspot.com/_OZHbJ8c71OM/TQSDVzivNyI/AAAAAAAAE...

Right, just curious as to why that old look since it's been a decade now. I was hard pressed to switch to 2.5 now that I recall late ~2009ish but never looked back. 2.49b was my first Blender version, been an expert user for several years now. Used to be heavily involved in the community some years back and now I moderate the stackexchange site over @ blender.stackexchange.com.

Also for pre 2.8, it was fairly non-trivial to get the UI to look like its predecessor as well.