Brian is the creator and original author, but he’s not the only one working on it any more. Ryan has been doing great work organising the creation of the Kickstarter stretch goals (I’ve had a few behind-the-scenes peeks and the adventure modules look great) and I’m sure that work will continue onto new projects when those are done.
Even should the final stretch goal mark the last official product for Open Legend, that doesn’t mean you won’t see any more content! The open source nature of the system means that anyone who wants to can create a product for Open Legend, and our wiki fills up with more and more free content every day. I myself am working on writing up a one-shot I ran to great effect at a recent convention, so look forward to that soon.
I do understand you concern, I share it too, but I think our wonderful community will carry the system through no matter what happens to Seventh Sphere