To anyone who finds this platform compelling and wants to help it to succeed: You can help by writing cross-browser mobile web apps, or by making sure your existing web sites and apps work well in Firefox as well as other browsers. Right now a huge number of mobile sites (including high-profile ones like Google!) use browser-specific code.
And if you are interesting in writing web apps specifically for the B2G platform, check out the new web APIs being proposed and implemented in B2G, and give us feedback on any that you use in your app: https://wiki.mozilla.org/WebAPI