I decompiled all of the jars and classes. If someone knows of somewhere I can post these files, I'd be happy to do so.
For anyone unfamiliar with decompiling: this is NOT the same as having the original source code. Among other things: many helpful variable names are lost, some syntax is lost, all comments are lost, and usage of enums are often lost. I still wish they'd update the download with the original source but I guess this is good enough for now.
On purpose we did not include the source code of the assembler, since it is a student project and we didn't want to make a complete solution available. Underneath, both the hardware simulator and the HACK simulator include within them the assembler code since they allow uploading assembly language code into the CPU. The idea was that if the student made the effort to dive into the source code, then we can let is pass, but we still would prefer a stand-alone solution not to be posted.
As an aside, I've written a tool to cross-compare multiple source code bases simultaneously, to find any similar code. I use it, amongst other things, to look for plagiarism in student submissions. At present, it can deal with C, Java or Python source code, but extending to other languages is not too hard.
If the assembly source code from the book's software was out there, this would be one way to check if students had "borrowed" it when writing their answer. But I also understand the authors' reluctance not to divulge the code.
Personally, I've already gone through the book cover to cover and am now converting the tools to C# and modifying them for personal hobbyist projects. The full source code for the assembler would be nice, but available disassemblers have worked well enough.