The text in your link claims: "it is illegal for a FORTRAN subroutine to call itself recursively, either directly or indirectly". That is not true anymore (for almost 20 years), since Fortran 90 has 'recursive' keyword with which you can declare that a subroutine can be used recursively.

(Also the all-caps spelling, FORTRAN, strongly hints that the link only talks about Fortran 77.)