Using GPL 3rd party code for internal closed source project
LicensingGplLicensing Problem Overview
If I use GPL software in my internal/closed source app do I have to make the source publicly available? say on the Internet?
Licensing Solutions
Solution 1 - Licensing
This question is specifically addressed in the GPL FAQ, and it says you're allowed to use GPLed software inside a company without legally distributing it. You have no obligation to release either source or binary outside the company.
You're talking about what Richard Stallman (the person behind the Gnu movement) calls "private software". For private software, any license that allows you to use the code works, because you're not distributing it. Both the Free Software Foundation and the Open Source Initiative maintain that it should always be possible to use software privately.
Solution 2 - Licensing
Loosely speaking, the GPL requires that you offer to make the source code available to whoever you make the binary available to. If the application is only for internal use, then this is probably not a problem, since you are presumably not worried about your internal users requesting or using the source.
Edit: Note that, to comply with the GPL, you're still obligated to offer the source code (even if no one takes you up on your offer), and you could conceivably get into dicey territory if an internal user insists on getting a copy of your source and you're not ready to give them one.
Edit: I did not realize that the GPL FAQ specifically excludes internal use from being considered distribution, which makes David Thornley's answer much better than mine. I guess I'll leave my answer since it covers the broader issue of limited distribution.
Solution 3 - Licensing
If you make nothing qualifying as a "release", you have no obligations under the GPL.
Personally using your own software certianly does not count. Giving some software to another group or division within the same company also does not count as a release.
However, time and use might cause some plans to change. It should be made crystal clear that any attempt to release the code outside of the company will require a GPL-compatable license.
Solution 4 - Licensing
Also, the version of the GPL that applies to the code matters. Version 3 of the GPL specifically addresses things like web services (where the user doesn't normally receive binaries), which Version 2 did not.