Yeah, the fact that you can't apply any mods (much less the SCP) to games on GameTap is an unfortunate limiting factor, but at the very least, a few people who play it there might be motivated to look around and learn more about it. The fact that we do have installers (albeit ones of questionable legality) here would help our case a little bit over that of Tachyon, I'd imagine. (By the bye, I'm just starting to work through Tachyon myself.
)
As for multiplayer, to the best of my knowledge, most GameTap games don't have it implemented as of right now, although I do understand that they'd like to change that in the future. At any rate, with the revival of PXO in the (hopefully) near future, we're more than set over here.
As for the idea of GameTap, basically, it's an online game distribution system run by Turner Entertainment. For a $10 monthly fee (which is discounted if you pay for larger chunks of time in advance), you get unlimited access to a wide variety of games (the current game library is somewhere around 850), everything from Atari classics to Splinter Cell to Sonic the Hedgehog to Zork to Deus Ex. You don't actually get permanent ownership of the games; instead, you download each game's data and run it through the GameTap client. It's a pretty nice setup; I'd been thinking of signing up for months, but what finally prompted me to do so was the launch of
Myst Online: Uru Live, which is only offered through GameTap. Another original property of theirs is the new episodic Sam & Max series, which is a great deal of fun. Unfortunately, the service is only available in the US and Canada right now (though Myst Online itself is available in several more countries via a stand-alone client), but I know they're working on expanding it.
As for GameTap having the rights to FS2, there are several other Interplay games on there (including Descent 2 and 3, FS1, Die by the Sword, and Planescape: Torment), so I'm guessing it's the same licensing agreement that allowed those games to be included. It won't affect the SCP in any way.