Does someone know if there is a site that shows on an all languages scale other still active root words?

Not for all languages, but for the major Indo-European ones there's always the online version of Pokorny's Indogermansiches Etymologisches Wörterbuch (link), but the interface is kind of sucky and I tend to use my offline version. Slowly, I have been collecting links to the major European online (monolingual) dictionaries and most of these contain etymological data. For Dutch, there is Etymologisch Woordenboek van het Nederlands (link), but you have to register. I also own Etymologisch Woordenboek der Nederlandssche Tal. I've had less luck with the various versions of Wiktionary, e.g., Dutch).

Dutch leuk is cognate with English luke as in lukewarm (see root *kelə- 'warm' in A-H link). (Interesting that tautology.)

Ceci n'est pas un seing.