by looking for free software every customer may use to manipulate the LAS point cloud generated by Pix4Dmapper I found the “LAStools” or also called " Isenburg Tools" after the founder of these tools. You can download the software from http://www.cs.unc.edu/~isenburg/lastools/
The usage is very academic but has a big variety of tools.
Hi Ulrich,
Thank you very much for sharing your findings with our community.
Best regards,