Is it available for vasp 5.4.x versions?

Vasp 5.4.4 is not compiling the extpot.F file, it is ignored.
There was not an extpot.F file in vasp 5.4.4 so I guess it will not work in older version of vasp. Although in the paper (10.1063/1.4922260 ) it is mentioned that this method was implemented in vasp 5.3.3.

Thanks in advance