ImageNest is a universal binary program built for Mac OSX in objective C.   It is currently compiled as a 32 bit application but is capable of 64 bit.  The primary reason for compiling as a 32 bit application is that no current commercially available print drivers are capable of accepting print jobs from 64 bit applications.

As soon as print drivers can accept print jobs from 64 bit applications it will continue to be compiled only as a 32 bit application.  This will most likely happen when PhotoShop becomes avaialbe as a 64 bit version.