"Android" and the GPL license: Is the Linux- adaptation by Google still free software?

The purpose of this seminar is to examine the nature of the GPL license and if the Android operating system meets the requirements for being considered free software. What is free software? Is Linux just a kernel? Is GNU the same than Linux? Does Android follow these principles? Why did Android reject the use of GPL license? Is the GPL license strictly necessary for Free software? Is Android Free Software or just Open Source? Can unofficial versions of Android become Free Software? These and many other other questions will be confronted in the next pages.