You mean like Positron? That was abandoned several years ago. So was Spidernode, FirefoxOS/apps, etc. Other dropped projects include Shumway, the JavaScript flash runtime. Basically every interesting thing they do that isn't directly related to improving Firefox seems to get dropped eventually.
Then there's GeckoView, which they explicitly decided not to make available as a WebView drop-in to be available systemwide on Android. In this case, at least they seem to have a reason, though it seems to me that having an alternative to Google's WebView would be valuable enough to continue.
Then there's GeckoView, which they explicitly decided not to make available as a WebView drop-in to be available systemwide on Android. In this case, at least they seem to have a reason, though it seems to me that having an alternative to Google's WebView would be valuable enough to continue.