[lug] GPL and Code Re-use?

[David Morris]

I have some software I am writing and would like to leverage
off of some GPL open-source software code that already
exists for part of what my application does.

To what extent is this possible under the GPL license?  Can
I use bits of code, or do I have to use entire
files/libraries?  How is the code properly attributed to its
source?  Do I recall correctly that new code I write would
have to be under the GPL license as well?

Related to all this, anyone know of a good guide to
open-source licensing (not in lawyer-speak)?  I haven't had
to deal much with licensing in the past, but I will in the
near future....

--David