Well, if the project sounds good, I am in...
My suggestion:
Code your own OpenSource OS. I have very little to none experience in that. 99% people will learn from that project. And yeah, if you can say that you have developed an operation system from scratch in colaboration... you have a very nice point at your resume. Also if the 'framework' has been coded it is easy to devide the work. Modules for videodrivers, sound, input, data processing, mathematical functions, graphical interfaces must be coded. And for this you do not just need time, for an OS from scratch that is worth it.... you NEED a team
What about it?



