Plenty of fonts with the same SIL open font license around already, especially if what you're after is a nice but generic modern sans serif font which 99% of users can't distinguish between.
Can't think of any reason why Nebula creators would go for this one other than to blend in with the platform's corporate house style for the 1% of users pedantic enough to notice and... well they could have picked an existing SIL open font for that if it had been about simply minimising creators' costs
I'd understand it way more if they were a big corporate creating something very distinctive and very closed source for their marketing material...
Judging from the kind of content creators nebula hosts I'd imagine they do in fact have the kind of nerdy audience that notices miniature font differences.