To be able to use the executables in a script or Custom Inventory Rule, the switch "-accepteula" needs to be added at the end of the command to accept the EULA. As an example, when using the "PsGetsid64.exe" executable, the commands would be the following:
For use in a script: C:\PSTools\PsGetsid64.exe -accepteula
For use in a Custom Inventory Rule: ShellCommandTextReturn(cmd /c C:\PSTools\PsGetsid64.exe -accepteula)