Yep, I remember the Archos tablets not having the Market because it wasn't licensed (or something to that effect), but there were some "leaked" Market apks so you could run it. These ran a bit too well to be leaked by a third party, but the point is that you can install the .apks in theory.
I just didn't know if they'd run on an x86 processor, so this is good news.
It's not "leaked", you can download the source code from Google at http://source.android.com/compatibility/index.html It's not licensed for distribution though, so unless someone signs all the license agreements, you'll have to build it yourself to be legal.
Market.apk bundles aren't device specific, so the one you installed was probably just ripped from some different phone/tablet/whatever... no conspiracy theory needed here.
The only hack needed for a decent experience is to either modify your system build.prop to make it look like a device that has real market support, or hack the Market.apk itself to make google's servers think your tablet is some device that it isn't.
If all you did was install the APK by itself, some Archos fan developer must have pre-hacked the market.apk in that way, but doing that is relatively easy and common and doesn't mean Archos had anything to do with it.
I just didn't know if they'd run on an x86 processor, so this is good news.