Good question. Do you mean this category?
http://www.cpdl.org/wiki/index.php/Cate ... ance_music
It is defined as:
"A list of music composed in the Renaissance era (ca. 1400-1600)"
Similarly, this category
http://www.cpdl.org/wiki/index.php/Cate ... _composers
is defined as:
"A listing of composers of the Renaissance era (ca. 1400-1600)"
"(If it is only a verbal description of the composers life time, it seems redundant to me).'
If this is a functionality you meant, I don't see how it's redundant. It allows users to have a place to go to peruse works written in the Renaissance, or a list of composers who wrote during the Renaissance.
I think even aside from the definition written, the terminology is consistent with users' expectations. If you or Eric Whitacre wrote a composition in the Renaissance style, it would not make the composer a Renaissance composer or the composition a Renaissance composition as most people would expect that categorization to apply. Did you mean something else?
So I think the category should apply to when the composer lived.
Regarding composers who span transitions between two adjacent eras (as also happened during the Renaissance/Baroque transition), I think both categories should be applied if the composer can reasonably be expected to be considered as having written during both those periods. If the composer was age 13 in 1610, then I would not classify them as a Renaissance composer, but a composer born in 1560 who kept writing to a fortunate old age should be listed in the two overlapping categories during which they composed.