It uses a distributed consensus algorithm to validate transactions. Anyone can run a validator node, and there are many companies/institutions out there doing that (Microsoft, MIT, etc).

The key property of Ripple you have to understand is that the consensus is decided by a set of nodes controlled by the Ripple team and their partners, and those nodes don't care about the opinion of any other node that's not on their whitelist. Everyone else just listens to what they decide the consensus is and follows along. While in theory you could listen to a different set of nodes, it'd be daft to: if those nodes ever come to a different consensus than the default nodes then you're screwed, and who you trust has no effect on who the default nodes listen to or how their consensus is formed.

They have no reason to use XRP though, they could just use the technology to launch their own token.

Yes, they can use any currency or crypto with the technology, but there still is a transaction cost. Using XRP will lower that by 30%.

>but there still is a transaction cost.

And that will be higher if they're using the same token that the general public are speculating on.