Free Software - What Is the GPL License?

In order for sofwere to remain free, it has to accomplish what he coined as the four freedoms. The g p l is quite strict, relatively speaking, saying that if you fork the project, your changes need to also be free software. They also need to stay under this same license. If you fork the mempl project and you add some feature, then the mempl open source project can take those feature additions that you made and merge it back into the Mempl project. And so that keeps the free sothwere free.