bryan over at Pipedot has released the source code for Pipecode, the software running pipedot.
Pipecode is written in PHP and the code is using the GPLv3.
I hope both projects are successful. They are written in 2 completely different ways but there is no reason why they both can't steal idea's off each other in the future. Scalability is always a concern for a large site and I think Slashcode has the edge here as it has had more time to mature but I am sure pipedot will learn and improve over time.
I'd agree with NC on the html output in the php, I'm a big fan on MVC type architecture.