The V argument is passed as an array of size 1.

...

This can have some surprising effects, if NV = 0, but the solution array would be declared as Y(NPDE*NPTS + 1) in the calling program. Here's the initialization routine that exposes the issue:

SUBROUTINE UVINIT( NPDE, NPTS, X, U, NV, V)
IMPLICIT NONE
INTEGER :: NPDE, NPTS, NV
DOUBLE PRECISION :: X(NPTS), U(NPDE,NPTS), TIME, V(NV)
U(1,:) = 0
U(1,NPTS) = 1
V(1) = 0       ! <-- eliminates effect of previous line
END SUBROUTINE

In practice this should be flagged as an out-of-bounds violation (or produce a segfault).