Anyone able to stream this video without flash?

"if (checkDevice()){
var nvb = new HTML5Video("http://video.golem.de/nvplayer/NonverBlaster_02-testing.swf","NVBPlayer10750video","620","349","9","#000000");
} else {
var nvb = new SWFObject("http://video.golem.de/nvplayer/NonverBlaster_02-testing.swf","NVBPlayer10750video","620","349","9","#000000");
}"

Very interesting. Maybe the site may play HTML5 Video

Well, first there is Gnash and (if Gnash won't work) Linterna Magica. Those are the standard way of doing things.

But there is a slightly more obscure way of watching videos than with Gnash (or other Flash-replacing plugins) and Linterna Magica. It's called Unplug.
It's a plugin that can be installed from within Abrowser, or when searching inside the Abrowser Add-On repository.

When on a site that doesn't show video, click on the Unplug symbol (sometimes it's hidden within the add-ons bar, press "ctrl + /" to enable it. On keyboards with German layout it effectively means pressing "strg + shift + 7".
Once the Unplug window pops up, you should see a list of available videos from this particular page. Rightclick the video you want to watch, choose open in a new tab. WebM videos usually play best within Abrowser. If Abrowser tries downloading this video instead of playing it, choose "copy link location" instead, open VLC and go to File -> open location. Paste the link, press play, enjoy. A lot of sites that seem to not be working otherwise can be tricked in this manner.

Sometimes Unplug lists the actual .swf files (those are the interface to the player and load the video url into it). I'm not aware of a way to play the videos in this case.

How about newer Lightspark versions from https://launchpad.net/~sparkers ?

$ sudo add-apt-repository ppa:sparkers/ppa
$ sudo apt-get update
$ sudo apt-get upgrade

(or, instead of "upgrade", "install lightspark" if it is not installed yet)

Also, have you tried other Firefox extensions to download Flash-wrapped videos? I don't know which are free or not.

The video can be downloaded using this URL (and then viewed with e.g. SMPlayer):
http://video.golem.de/files/1/1/10750/metrolastlight-sd.mp4

P.S. in order to find this URL I used Lightspark (version 0.7.2 which I compiled myself on Parabola GNU/Linux) and Wireshark and searched in Wireshark "frame contains .mp4". The output was the part "GET /files/1/1/10750/metrolastlight-sd.mp4" and host "video.golem.de" which I combined to create the URL.

Thanks to all your great advices, I have found the (for me) best solution at the moment:

1. Lightspark installed
2. Linterna Magica installed (unfortunately, with linterna magica, there appears this bug from time to time: https://trisquel.info/en/forum/en-fin-dadresse-url# so I have to turn it on and off)
3. VideoTube installed (like linterna magica, also a greasemonkey script)

golem.de runs with lightspark (very buggy but it seems to work sufficiently good), the other site (4players.de) runs with linterna magica and the non-html5 youtube videos also work with linterna magica.

To sum it up, linterna magica filled the gap!
I have to test this for a while, perhaps some bugs appear.

Abrowser and Firefox do not at this time, but the Chromium browser with the "chromium-codecs-ffmpeg-extra" package will:

https://launchpad.net/~cmiller/+archive/chromium-browser-stable-daily

Some of the videos on the golem.de website use the .flv extension, e.g. this one about the Neo Freerunner:
http://video4.golem.de/files/1/1/1559/neofreerunner_mw_on2.flv
To find the URL using Wireshark just search for "frame contains .flv" instead of "frame contains .mp4".

Do this:

0. Shockwave Flash plugins (Gnash/Lightspark/Flash) must be disabled from Abrowser's Add-ons Manager
1. Go to the webpage with the video you want to play (e.g. http://video.golem.de/games/10750/metro-last-light-test-fazit.html)
2. In the place where video should appear, there is a title of the video and just above that a tiny little fracture of an actual image. Right-click on it, and select View Background Image
3. Modify the URL of the image by replacing teaser with files, then rename the filename from QUALITY-HEIGHT-TITLE-AUTHOR-ANYTHING.jpg to TITLE-[sd|hd].mp4 and press Enter.

This way, you will be able to watch videos right from your web browser. Note, that this hack doesn't always work because the image name can be different from the video filename.