There was a time when Pixel gave out the source code for Cave Story to those who could create a working demo of their port of choice. During that time no-one ever asked for the source code for Ikachan. Now it is likely too late. If you want a PSP port (or any non-windows port) of Ikachan you will need to manually reverse engineer the Ikachan executable. Fun, no?
Although there is a commercial 3ds port if you need some Ikachan on the go.
Assembly is the textual equivalent of machine code as it is executed under that platform's native instruction set. It is not by any means a portable language because for example the instruction set of the PSP is vastly different to that of a Windows PC.