Dear blackbird71
I just add what I told about Chromium licences in Firefox in 3rd post of this topic:Dear blackbird71:
I don't know why I have a memory about Chromium license in Firefox.
Currently, there seem to be 7 web browser engine variants still under active development: Gecko (Mozilla Firefox), Edge (Microsoft), WebKit (ancestor of Blink - Safari), Blink (Chrome, Chromium, Opera & many others), Goanna (forked from Gecko - Pale Moon), KHTML (ancestor of WebKit and Blink - Konqueror), and Servo (Mozilla experimental). Olde Opera's Presto has joined a growing number of dead browser engines no longer being developed by anyone. When one boils down the ancestories into families, there are really only 3 unique families of browser engines still under development: Gecko, Edge, and Webkit/Blink/Goanna/KHTML (with Servo yet to see the light of day in the non-lab world).
There's a reason for the small number, and it has to do with the costs of engine development and continuing support in a rapidly evolving Internet world. You were correct earlier: the smaller the array of engine choices, the more limited will be the feature sets compatible with the engine API's, hence the more similarities between browsers built on in-common engines. Unfortunately, that observation will make no headway against the economic pressures acting against totally new engine development. With the entire Internet model now built around 'free' products and services, browser/engine development and support costs will continue to exert irresistible pressure for browser makers (like Opera) to adopt already-existing and supported engines. At this point, all users can do is make the best choice for themselves from within the universe of available browsers. We can look back fondly at this or that feature set or capability of browsers no longer in production, but at the end of the day, we must deal with the world that is, not the world that was.