What were the motives behind changing the license between PHP 3 and PHP 4?
Suraski: There were several reasons. The main concern with the GPL was that commercial companies, such as IBM and others, avoid GPL’d code like the plague. The fact that the GPL is “contagious” discouraged many companies from putting effort into projects that are distributed under it. If we take a look at the few open source projects that IBM endorses, we would find Apache, Jakarta and PHP – none of which is released under the GPL, and we believe it is not a coincidence. These licenses are less restrictive, and we believe they work better in the real world. We also felt PHP was mature enough to let everyone use it, without having to ask for our permission, which is why the permission clause was dropped. Other than that, the license stayed pretty much the same.
