You are using the word vaporware in a very odd way. Vaporware is stuff that won't actually come into existence. Vivaldi has already been publically available for nearly a year.
If it was a closed source project you'd have to start from scratch every time if you wanted to restart the project.
It is not unheard of that someone tried and abandoned but would probably have achieved their goal by starting from scratch rather that attempting to revive an outdated unmaintained project.