There are a pretty large number of "serious" companies that distribute code under the GNU GPL, which has similar but more stringent copyleft terms. IBM, for example, which also originated the Eclipse Public License, and TI, and ARM, and Apple. Almost every microcontroller vendor uses GCC.
I meant "product code" mostly, and of course you could say WebKit is part of a product and you'll be correct. My point is that it's the exception, not the norm. (Using "no company" was wrong on my end)