As far as I know, all of Haiku is currently open source software, but it isn’t all free software. So if you are an open source advocate (as opposed to a free software advocate) then there’s nothing to fix. 
For anyone who would like a very brief description of the difference between the two: Open source software is about using the best technical solution. Free software is about believing that software that protects a user’s freedom is more important than anything else.
Because of Richard Stallman’s then recent work on the GPL and the FSF, Linux torvalds decided to use the GPL. It is believed that the success of Linux and the explosion of free software available would not be anywhere near what it is today without the work of the FSF. (See: “Revolution OS”) To further add to what I’m trying to say, here’s a simple point: the work of both Richard Stallman and Steve Jobs are widly loved and widly disliked by large groups of people. Regardless of anyone’s feelings though, it’s hard to deny that both have had a huge impact on the computer industry.
…Since this topic is specifically about free and open source software, I thought this would be a good place to be pedantic. I hope my answers are not antagonistic. This is just a topic I love to talk about. Please forgive me! 
…Oh, and as for Haiku, I don’t think any change in license is necessary. It’s doing great the way it is.