Even so, it’s going to scare off a lot of potential contributors long before they investigate the language deeply simply by having a name they don’t recognize. It effectively limits the contributor pool to those who’ve previously written GTK apps, which is relatively tiny compared to the number of devs coming from more mainstream backgrounds.
I was looking through some of their sources, and that was the first encounter I’d had with Vala. If anything, it makes me more interested in potentially contributing.
Now, whether the tooling is up to snuff is another question. If it’s not, then the language choice could still end up being a turn-off, if not an immediate one.