In laymans terms, binaries are the files a computer needs to run the program. Right now, 5.0 is NOT AVAILABLE in its binary (usable) form. BUT if you have the correct knowledge and software, you can create your own binaries and get a semi-complete 5.0 going. Otherwise, you need to wait until they (the ever more respectable developers) finish the 5.0 version, and release it in a usable form to the public. That way you don't have to worry about binaries, what they are, or what to do with them.
They don't have a date of the 5.0 completion (unless I somehow overlooked it while storming the boards), but from what I've read and experienced it can't be too far off.
Edit: P.S. The binary form is what you recieve from compiling the source code with Visual Studio 6.0, or .NET. I assume it's possible to have accomplished this, and still not know what binaries are. If you have compiled the 5.0 code, you HAVE the binaries. :P