This seems quite positive to me: Clearly the rightsholders are not being total jerks since they're happy to allow an OpenTTD bundle, and the original game is available with modern fixes as well.
> If you already own OpenTTD on Steam, nothing changes. You’ll continue to receive game updates as usual. If you ever need to re-download the game, the game will remain in your Steam library.
This part of the announcement was nice, too. It would suck if existing users had it deleted from their libraries.
Given the “rightsholders” have no rights over OpenTTD (only the assets are copyrightable, and OpenTTD has had its own set of open-source assets for the past 15 years), I can’t agree with this.
I’m not sure how to interpret this other than Atari not wanting to compete with OpenTTD on Steam.
More likely they were jerks and blackmailed openttd into bundle on the threat of forcing them off steam altogether.
I kind of doubt that. Chris Sawyer is on record being really hostile to open source reimaginations, especially OpenTTD (and it's just a reimagination at this point as OpenTTD shares no assets or code with it's predecessor). It wouldn't remotely surprise me if Atari was putting legal pressure on the OpenTTD devs.