:o) It's back!
Only took 8 years (happy dance)

This is version 1.10 with no community beta 1.2 patch.

Too bad for WeGo/H2 Entertainment, I've already moved on to RVGL with the assets from my original CD from 1999.

Is it necessary for enjoyment to use RVGL, and can it be used with this GOG version?

I'd say so, yes.
It brings up to 12 players in online races and supports 4 player split-screen local races.
Plus all the fixes and features from 20 years of community patching and also supports a full integration of the the Dreamcast exclusive Rooftops track and 14 cars.

Yes, RVGL is just a patch. You need the original game data and music from a legit source like GOG or the original CD.
However, there's still plenty illicit sources, since the game has been in abandonware limbo for 20 years.

Find everything you need here:
https://rvgl.org/

(You'll find the Dreamcast data there as well, since I guess that one is pretty much not available anymore anywhere.)

Thank you. I'm happy to buy from GOG as long as I know RVGL can work with it.

No, not _necesscary_. Enjoyment can be achieved with the vanilla version.

Maybe that's a stupid question, but where will my money go if I buy the game? I want to buy Re-Volt but I don't want my money to go to scummy devs who used community work as their own for profit.

The current owner of the Re-Volt license is H2 Interactive, a Korean licenser/publisher.
http://www.h2int.com/about/about.html

Seems like the previous company WeGo, who made the crappy mobile version cash grabs, and who illegally used the community patch for the first release on GOG in 2013, went out of business and H2 Interactive bought up the scraps.

They're definitely smarter, by releasing only the version they really own on GOG.