The stuff at https://github.com/besm6 is great! Being much later, the programs are substantial, but it gives a better sense than the simplified examples like https://github.com/xldenis/besm/blob/master/examples/chapter... .
For that I actually copied the pages of the book into the the comments of the code: https://github.com/xldenis/besm/blob/master/compile-pp/src/B...