Hi you can grab the game for cheap on Steam.  If you prefer the original CD version, there are places *ahem* where you can grab ISO files to install it.  Keep in mind that if you do this, most downloads I've found are the UK version and so you'll need to get the UK 1.6 patch instead of the US one.

Don't worry about a UBISoft ID or a CD key.  UBI shut those down; now you can install the OpenRVS patch (after patching to 1.6) and then multiplayer works without those requirements.