The imglib2 ArrayImg class is limited to storage that holds a maximum of Integer.MAX_VALUE elements.
imglib2-unsafe is an effort to create ArrayImg like Img objects that can store elements beyond that number in a single contiguous chunk of memory.
In addition to that, arbitrary memory pointers/addresses can serve as data backend through sun.misc.Unsafe.
It is the callers responsibility to ensure validity of the accessed memory.
Many of the classes, with the exception of any that use sun.misc.Unsafe, in this package could be considered to be added to imglib2 core.
An example use case for this is imglib2-imglyb, a python-to-ImgLib2 bridge that combines Java and Python through JPype (JNI).