Maciej is a freelancer working mostly on PyPy for the past several years. He's a core developer since 2006, working on all kinds of parts in the entire codebase including JIT, GC and assembler backends. Maciej has been going to many conferences, advertising PyPy to a broader audience for the past several years, including a keynote at Pycon 2010. He's also the main maintainer of jitviewer, a tool for analyzing performance of your python programs under PyPy.