I used to develop Set Top Box user interfaces that used the Ekioh browser. We'd use SVG, JavaScript and CSS to get native UI performance in a browser that was running in 256MB ram. Their later versions enabled us to use HTML5 and CSS3. I enjoyed the challenges of balancing UI animation against capturing keypresses and other events as well as executing JavaScript fetched via AJAX. Due to the memory constraints we couldn't use any JavaScript frameworks and wrote everything in vanilla JS.

Our C and C++ developers would expose the native hardware functionality up into the JavaScript Ekioh engine so that we could access and control features like scanning cable TV frequencies and recording to disk.

The cable and satellite TV networks would end up paying a licence per instance of the browser running on each of their customers set top boxes.

Curious what does your question imply? DuckDuckGo, Google, Safari, Instagram are all examples of closed source software and have no problems reaching users/customers.

Anyone who wants to run a high performance browser on minimal hardware. Eg browser on TV set top box, embedded point of sale device, etc.