I hope they don't ban GE: Source by law...
HL2 is rated 18+ so i don't think they can restrict this any further, and there is no law against modifications so far.
In fact allmost all the ppl who decides about these kind of things, don't even know it is possible to modify a game.
So their focus is on the commercial products.
BTW: GE64 never came out officially in germany, but it's also on the so called "index".
There are two lists A & B.
Media on list A are forbidden to advertise in any kind, most magazines desn't even write their names course it could be seen as advertisment and the whole issue of the magazine could get seized.
This happened once with an issue of the german videogames magazine "TOTAL",when they printed the MK dragon on the cover.
Goldeneye was named Silvereye in the 64Power, course it was on that list, too.
List B is even worser, media on that list are forbidden to sell and also to import from other countries. You can be punished for selling such a game/film/book/whatever or to bring it into germany from beyond the border.
The only thing that's still alowed is to own it, but you are not allowed to show it to someone else.
So if you wanna watch this Film, play this game with friends, theoretically it's illegal and if someone ever find out you can be punished too.
Now you see how far it has allready come, and all in the sense of protecting our youth.
Don't get me wrong, i'm absolutly for protecting them but not at the cost of the mature gamers.
There are forces in the politics which would like to see a law against the production and distribution of so called "Killergames" (which means ego shooter).
There are phrases like: These kind of games were invent by the military to practice killing and lower the threshold for killing someone.
They blame these games for things like ammok in schools (e.g. Erfurt). The politicians were trying to seize CSS, but the USK (an institution which rates games, much similar to the PEGI) gave it a 16+ (german version, no blood, dead hostages sit down instead to die, enemies disapear after death... the regular BS), so it couldn't be restricted any further, at least the german version.
Some of them are trying to replace the USK with a new institution, course they feel they are rating games 18+ which should be forbidden.
Nazi Revolution: All the signs of the Nazis are forbidden here too. So games with WWII theme will be censored too. So there will be replacments of the symbols on flags, german soldiers don't say certain sentences anymore, and so on.
At the end i don't think the hard censoring is related to much to the NS hiostory, it's more the conflict of generations.
I mean it was the same when TV came first, they said it makes you silly, Better read books.