I've always felt bad for windriver; they do a lot of good work and there are clear benefits but because linux is free people keep moving away from their products. It's cool to see them doing more RISC-V stuff though

There's also Green Hills, which has a far better product (Integrity) vs. WRS VxWorks. Somehow VxWorks has better marketing and more sales, because their product is cheaper.

Both are commonly used for space-borne platforms, and I've done development for said platforms with both.