@Horun: you're both correct and not! Let me elaborate - why:
So, what Terratec published on now long defunct website "linux.terratec.de" is not technically driver made by them, but by the Taiwanese company manufacturing the device for them - I don't know if that company still exists, but back then their website was "www.ame-group.com" - hence why the file published on the Terratec website is named "ame_linux.tgz".
If you look at Archived copies of "linux.terratec.de" (unfortunately those copies did not archived the file in question "ame_linux.tgz"), 2 things become clear:
1) when Terratec is not the publisher of the driver (i.e. it's not made by them or any of their OEM companies manufacturing the device for them), then they just put a link to the 3rd party website, open-source driver project page, forum, etc. where the driver is located
2) when Terratec or their OEM company manufacturing the device is releasing a driver they made, then Terratec hosted it to "linux.terratec.de" exclusively.
further more, what I am calling the original Terratec driver "ame_linux.tgz" is released earlier than the not working (for me) LinuxTV driver to which @vetz pointed out and gave a link to.
So, in very short there are 2 drivers:
a) "ame_linux.tgz" - currently lost, made by "www.ame-group.com" for Terratec, relased by Terratec on "linux.terratec.de", called by me "the original Terratec driver".
b) what @vetz linked to, i.e. "community"-developed open-source driver for TM6000, not properly working with my Terratec device, in fact not working at all.
I have very little hopes the "ame_linux.tgz" will surface, but without it, then at least Terratec TM6000 devices are just paperweight if you want to use them in Linux.