Local File System Access (LFSA) is:
Client Side Web Apps run solely on your device, they are not related to cloud solutions in any way: nobody can pull the plug on you. CSWAs may use LFSA to keep data locally so that you could have complete control of your data.
PSKOV static site generator is the first CSWA to use LFSA.
Download lfsa_1.0.0.py.
If you use Linux or macOS, you're all set.
Windows doesn't have Python installed by default, you have to install Python yourself to be able to run LFSA.
Note: the video depicts Python 2.3.4 installation under Windows 2000, use the latest Python available for your version of Windows.
If you use Linux or macOS, run LFSA in terminal:
/path/to/lfsa_1.0.0.py /path/to/dir
If you use Windows, run LFSA in CMD:
C:/path/to/Python/installation/python.exe C:/path/to/lfsa_1.0.0.py C:/path/to/dir
As you noticed, LFSA can run on really old operating systems dating back to 2000. That's intentional: we care about users, so we want to cover as many users as possible.