I worked at Nokia when management stubbornly kept flogging the dead horse that was Symbian. It didn't work. It just wasn't good enough. Android, even in it's early versions was hardly perfect but still ran circles around Symbian. Android at the time had issues with stability, features, performance, etc. But it was a breath of fresh air compared to Symbian devices which had even more of those type of issues. And of course the iphone redefined what a smart phone should be around the same time.
Nokia actually opensourced it around that time as well. Symbian has been open source for well over a decade. This looks more like the retirement of what remains of that effort, which included the Symbian Foundation. Presumably, by now there are very few; if any, commercial users of Symbian left. So, they are parking the source code at Github for whomever still has some use for it. As you can see from the commit logs, development has been dead since 2010. I seriously doubt that is going to change.
Nokia actually opensourced it around that time as well. Symbian has been open source for well over a decade. This looks more like the retirement of what remains of that effort, which included the Symbian Foundation. Presumably, by now there are very few; if any, commercial users of Symbian left. So, they are parking the source code at Github for whomever still has some use for it. As you can see from the commit logs, development has been dead since 2010. I seriously doubt that is going to change.