Back in ... 1991? I did use the C version of the Simplex Method almost straight from the book. I needed a concise linear programming optimization module that would be called in the middle of a not-really-concise production programming system handling (automotive) engines and gearboxes production for a couple of FIAT plants.
Basically a short-period scheduler to decide what to produce (slave to an immense system running on IBM mainframes; COBOL, again).
So I quickly put together the C version (with minimal modifications) and it chugged along happily on a VAX for at least a decade.