That looks like the brainfuck mandelbrot set by Erik Bosman, but the example is missing the header line with the credit. The one I saw came from here:

https://github.com/thaliaarchi/bfcorpus/blob/main/ebosman/ma...

Be sure to check out other files in that directory for how the program is assembled.

(Erik Bosman's mandelbrot set is a personal favorite of mine, very useful for benchmarking brainfuck interpreters)