Sometimes when I'm not blogging it is because I'm hacking code. This web controlled realplayer is one result. Probably of limited interest to most people but who knows. Anyway it does illustrate a few things about the Open Source/Closed Source debate.
On the plus side: Open source is empowering, in that it enables the user to make whatever changes he wishes and propagate them on, thus the development of the project is not limited to the resources or interests of the original creators. My open source app is an example of this. I am reasonably satisfied with the web interface I have but someone with 100s or 1000s of tracks will probably want to see some improvements and with an open source program it is easy to do so. However on the minus side: my app will almost certainly not run on another person's computer without some changes and I have no incentive to make it any easier to use. This illustrates the downside which is that much open source expects the user to tinker and thus be knowledgeable and thus it is less user friendly than closed source. Another good example might be Skype which is (relatively) closed source compared to say the Asterisk project, but which is widely used.
However the closedness of the source code is somewhat immaterial. What is important, in general, is the closedness of the API. Skype is, in this regard significantly better than the Helix/Realplayer development which is Open Source, because Skype have clearly published their API and have made an effort to provide a place where skype users can find third party products using that API. Skype therefore combines some of the benefits of open source with some of the benefits of closed source. In fact the "Gorilla Game" book makes the point that one of the necessary pre-requisites of massive technological domination is an open proprietary platform precisely what Skype offers and precisely what Real doesn't quite manage to do.