As already promised some time ago, the Newton Game Dynamics Engine is now also available for Linux. You can grab version 1.32 of the SDK here (also includes all tutorials).

As for the Pascal/Delphi-Headers : Since they are now maintained mostly by myself they're not available for Linux. I'm no Linux-user (although I have a distro installed somewhere) so I haven't ported/tested them under Linux. The headers itself (get them here) work with FreePascal, so they may also work with Linux out of the box. If that's not the case and someone wants to port the header to Linux, please contact me!