I’d rather see more open source projects making something new than so much “Open Source reimplementation.” If closed proprietary companies are so worthless then why do so many open source projects copy those implementations. Did Wolfram really discover the one true way in its language syntax and presentation layer? If it did, is the idea of open source really just making it unviable for companies to invest in important things like that? To be clear these are of course rhetorical questions. The open source world could experiment (and in defense sometimes does) with truly new approaches and interfaces. I just want to see more of it.
Mathematica exists. Mathematica for free versus Mathematica for money is of course a nice trade. But even better would be to try new ways to interact with mathematics unburdened from legacy concerns.