Okay, so I have a lot of new information on this, if anyone's interested. I've been trying to get this pulled off for some time, as a non-G1 user myself.
First of all, the Android Market is *not* built into the OS; it is actually an APK file which can be found in dumped ROMs. This one should be adequate (look in /system/app or similar, it's "Vending.apk"):
http://rapidshare.com/files/155612986/Android_dump.rar
However, you cannot just copy it into an arbitrary Android installation, emulator or third-party port, and have it run. The main problem is that there is no classes.dex inside the APK. Instead, the binary classes are stored in an optimized "Vending.odex" file in the same directory as the "Vending.apk." However, this optimized file depends on other optimized odex libraries which do not exist in the same folders on the emulator as on G1. The ODEXes may also be platform-specific in terms of optimizations.
This document provides more information on the whole dex optimization issue:
http://mirror.nytes.net/programming/and ... exopt.html
Now, if we want a way around these obstacles, I did contact someone else who was working on a possible solution. They have uploaded hand-modified DEX and APK files, but they do not currently work:
http://strazzere.com/blog/ is the person's site.
As for Google themselves, apparently they want to maintain total control of the Market. They intend to open up a Web-browsable interface, but no downloading whatsoever outside of their sphere of control. This is not an approach that I am willing to tolerate, so I am doing all I can to get these things to work. The Market is closed-source and G1-exclusive, so outside of these leaks, there is little else that can be done.