I already saw the notice concerning the removal of the games from the catalog, but why have they been removed ? I'm just curious.

Interplay has sold the rights to another company (Bethesda), and their contract with GOG expired 31st december 2013.

Thanks for the answer.

GOG was awesome and was giving away free copies of F1, F2, and Tactics during their winter sale. I was lucky enough to pick them up for free before they were taken off. I've never played them before so couldn't be a happier GOG customer!

Unless GOG will sign a new contract with Zenimax (Bethesda's owner) or with Bethesda itself, there will be no Fallouts.

Actually, the full story is this:

In 2004 after Fallout Brotherhood of steal bombed and black isle closed, Interplay wanted a AAA developer to make the next fallout. Interplay licensed to Bethesda the rights for 2 numbered entries and 1 spin off (Which only of them, Fallout 3 and New Vegas have been made).
Later on however during development of Fallout 3, Bethesda bought the franchise around 2007, but part of the deal was that:

1. Interplay would retain rights to sell Fallout 1,2 and Tactics
and
2. Interplay could develop Fallout Online, a project that had been in ongoing concept phase for years prior to that.

Bethesda agreed to those, but imposed a limit. Basically, Fallout Online was required to be completed by 2012, or else Interplay would breach contract. Interplay never completed the game, so a large lawsuit was filed. Bethesda won and Interplay lost rights to Fallout Online and it was cancelled.
Out of grace, Bethesda allowed interplay to retain rights to Fallout 1 and 2, as well as tactics until December 31st 2013. After that, Bethesda would be 100% owner, and interplay would no longer have any ownership what so ever.
So, as of Jan 1st 2013, that happened. Due to the trademark and legal rights switch, all distribution and retail channels were required to pull it. Bethesda has final say as to whether or not the trilogy will appear on a site.
Bethesda is not to blame here. It was legal issues that made them be pulled from GOG. Chances are they might return. Bethesda loves money, and I am sure they would love to milk these games as much as possible. They are getting them re added to steam, but I am sure they will get them on GOG to double the income from the 3 titles.

you are wrong: Bethesda is to blame here.
why do you think Fallout was put for free at the end of december?
who do you think has paid to GOG for the free copies???? the poor Interplay? I don't think so, hehe.
the terms of the change of ownership of the franchise were known since months and do you really think GOG hadn't tried to find an agreement with Bethesda in all this time???............

Well I'll be more interested in Wasteland 2, what is supposed to be like Fallout 3 if it had been an actual continuation
of the F1 and F2 style gameplay... Graphics-wise more advanced of course.
Supposedly if it all goes well the game is coming out before Summer...?
The Steam is selling already for a golden sum an early-access beta.
There is interesting stuff going on in the Inxile Wasteland 2 forum...
As someone who had played the beta recently demanded more features for char-dev and combat :)
Not that F1 and F2 weren't great - having completed them really is the reason to be excited about W2.
And just as a side note to who may not know: Brian Fargo is part of the W2 dev-team.

If you have the 3 games already on your account, are those games still available for download if you change computers, or do I need to make sure I backup my files extremely well?

Excerpt from official thread, posted by GOG.com:

But New Vegas already was made by Obsidian Entertainment (ex-Black Isle minus Brian Fargo)

And Wasterland 2 by Fargo already have beta and preorder =D.
But i would never buy something from "Rabscuttle's steamer" while it have 300% margin depend of region policy (hello from ARMA3)

ps. I'm very glad that gog reacted this way. Our central game media announced this with delight)

Actually he is referring to the original Fallout 3 that was in development in 2004, not the project that came out in 2008.
Look up Fallout 3 Van Buren for more info on this.

Anyways though, from the beta I played of Wasteland 2, it plays nothing like Fallout 3 Van Buren. It plays more like Tactics instead.

Wasteland 2 may seem more similar to the classic Fallouts because it's a sequel to Wasteland, which is now sold under inXile as they acquired the Wasteland rights in order to develop Wasteland 2. And why do I say being a sequel to Wasteland makes it similar to Fallout 1 and 2? Because both the series have always been having copyright and ownership licence issues, and when Black Isle tried making Wasteland 2 back in the day, EA owned the rights to the name and they made a spiritual successor instead -- Fallout, which would go on to start its own series.

The Wasteland series are more tactical and squad-combat based, though, so I would argue that they look more like Fallout Tactics in terms of gameplay, albeit being more close to Fallout 1 and 2 in terms of content, writing and overall story.

This:

http://fallout.wikia.com/wiki/Hervé_Caen

How I see it, and it's just a wild guess... But As I see it from what I have read Fargo's writings in the internet...
It's not so much the matter of the title of the game. It's about making a game that fans and he likes.
All that we-own-the-rights-of-that business could have destroyed the chance to make Wasteland 2 as it is coming out now.
Not that there is anything wrong with this attitude. I'm sure even more business oriented people make alright games, even great games.
It's just that some people like something :)
btw. My wish was just that with some luck, some day the W2 would appear here in Gog.com and be an amazing
gaming experience, win-win for Inxile, Gog, and the gamers :)