As in software that’s licensed under a open source copyleft license, but costs money to run that’s beyond an optional request for a donation. I can see this happening with libre hardware since it still costs money to manufacture even if the design is free, but with software, wouldn’t someone immediately fork the project to remove the payment requirement?
FOSS tends to be paid for beforehand or for support.
RHEL, for example, provides an excellent OS with support.
Godot provides anyone with the ability to make games, but when a big company wants it extended so their game can be better, they pay money upfront, so the Godot team is - for those companies who want more - free as in ‘free speech’, but they also pay for work.
Lastly, for the sake of completeness, there are games which were paid for, and later gained a GPL licence.
People have mentioned ‘donations’, but I’m not sure if that amounts to any real development. Maybe it does, but the so-called ‘donations’ to the Linux foundation aren’t typically charitable, but made by corporations who use Linux to make money, so they’re more similar to Godot than actual charity.