I'm no math expert, but I like Core Plus. In fact, it was a brouhaha over the proposed adoption of Core Plus at Coventry (CT) High School that led me to discover the Coalition of Essential Schools ten years ago, go to Brown, and in other words start me down the path to where I am today.
Someday, when the NSF gives out money for a project like Core Plus, it will be a stipulation that all the materials be released under a free content license, and then people like Dan Meyer will be able to take their lessons, which are probably about 80% of what he wants, add a little dy/dan sex appeal, redistribute his own version, customized for his local standards, yadda yadda yadda.
Someday. We're getting closer though. Inch by inch.
Also, we need a bridge between these US academic developers and Linux distributors. Open source in education advocates wonder where all the good software is, and when it is written and freely licensed, it is often kept secret.