It is a common myth (propagated by anti-GPL activists) that using GPL'd code in your software requires you to put your software under the GPL. In reality, your code can be under nearly any open-source license.

I often receive emails from users asking me to re-license one of my libraries from GPL to BSD/MIT so they can use it in their own open-source projects. These users are often confused when I tell them that they can have a BSD/MIT project depend on GPL'd code.

Everyone who cares about the health of Free software (and open-source in general) should be careful not to fall prey to this misinformation campaign.