There's nothing wrong with forking, and it's clearly allowed under the GPL licence, and is legal and above board. But there are good reasons for forking - for

There's nothing wrong with forking, and it's clearly allowed under the GPL licence, and is legal and above board. But there are good reasons for forking - for instance, if the code has languished for ages, and there are forks which split the potential development and user community. There's always two sides to every story, and I'm involved with Jigoshop, but certainly Jigoshop/Jigowatt supported a team of developers to work on a project which resulted in two of the team leaving just as the stable version was about to be released, there was a low offer of acquisition of copyright of the product, and an offer of collaboration which had certain conditions attached to it, so would not have been workable, and forking is being used as a business mechanism, rather than a method of evolving the software