Yes, you can find svpflow1/2.dll in plugins folder from SVP 4 Free installed.
I will look what I can do to make GDF scripts compatible to avisynth 2.6
My file version is 2.0.2.0, size 647,680
Last svpflow2.dll from SVP 3.1.7 has version 2.0.3.0. You can get it from SVP 3 folder. Or you can take file linked below.
Try it. The error can be fixed there.