[module0000]

Not sure what the OP's motivation are for asking "why GPL?", but my motivation when I ask that can translate to something like this:

"Hi, I'd like to use your library, but your license is incompatible with the other <N> licenses in my codebase. Consider BSD please?"

[llukas]

It's not like GPL v3 prevents guy from contacting the author and offering him $ for license.

[protomikron]

"Don't ask the author of a library why it is incompatible with proprietary licenses. Ask why your codebase is incompatible with open licenses."

JFK