The “Yzena Copyleft License” states that it's a copyleft license, but it also states that it's not a viral license. According to Wikipedia, a viral license and a copyleft license are the same thing.
There is a difference between "strong" copyleft and "weak" copyleft. An example of "weak" (non-viral) copyleft is the CDDL. In fact, the CDDL's Wikipedia page talks about strong and weak copyleft.
You can read [1] for a breakdown of copyleft by an actual lawyer. Suffice it to say that Wikipedia's Copyleft page is woefully inadequate.
