LPILE Plus 6.0 could be downloaded from the developer's website when we last checked. We cannot confirm if there is a free download of this software available. The program lies within Photo & Graphics Tools, more precisely 3D Design. This software is a product of Ensoft, Inc. We recommend checking the downloaded files with any free antivirus.
From the developer:
LPILE Plus is a special purpose program based on rational procedures for analyzing a pile under lateral loading. The program computes deflection, shear, bending moment, and soil response with respect to depth in nonlinear soils. Components of the stiffness matrix at the pile head may be computed internally by the program to help the users in their super-structure analysis.
You may want to check out more software, such as EasyPlan, VFDS or DesignCAD Express, which might be related to LPILE Plus.