More to the point, as a software engineer, or code monkey, or code master, whatever, you should be well aware that if it's code you didn't write, don't use it until you're clear as to the ramifications.
I avoid using any example code I see unless I can understand it and there's a clear statement of "Hey, this is example code, by writing this tutorial, we kind of expect you'll be making a derivative of it."
Treating GPL-licensed code (or some open source license) under the same regard is poor thinking. Passing it off that some manager will catch it is worse.
That strikes a little too close to "Sure, I plagiarized my college essays, but I didn't get caught, so I must've done the right thing." Unfortunately, fair use has not been well-defined with source code (or, anything, really), so where you could poke a hole in that analogy with "But I made appropriate reference!" (i.e., telling the person that paid you to do the work), becomes very fuzzy, very fast.