As many have pointed out it was very easy to develop for. The developers of Dead or Alive 2(Tecmo), one of best looking 3D fighters on the Dreamcast state stated that developing on the Dreamcast was like writing a sentence with a pen whereas on the PlayStation 2 it was like writing a sentence with a brush.

People are still developing games for it using open source libraries. There was recently a 3D racing game released.

https://www.kickstarter.com/projects/pixelheart/arcade-racin...