I found a project on GitHub that I really liked, and have since forked and modified it. It's currently licensed under Apache 2.0. Can I release my modified project as a project with a new name under GPLv2? If yes, how would I credit the original contributors (aside from preserving git history)?
Unlike the BSD, MIT, and ISC licenses, the Apache 2.0 license is not compatible with the GPLv2.
Despite our best efforts, the FSF has never considered the Apache License to be compatible with GPL version 2, citing the patent termination and indemnification provisions as restrictions not present in the older GPL license. The Apache Software Foundation believes that you should always try to obey the constraints expressed by the copyright holder when redistributing their work.
Please note that this license is not compatible with GPL version 2, because it has some requirements that are not in that GPL version. These include certain patent termination and indemnification provisions. The patent termination provision is a good thing, which is why we recommend the Apache 2.0 license for substantial programs over other lax permissive licenses.
If you want to prevent others from keeping modifications to your code to themselves, you can relicense under the MPLv2, the EPLv2, or the more restrictive GPLv3 instead. This will also prevent the original project from using your improvements though (unless they drop the Apache license too), so that may not be very nice towards them.