Earlier quoted context omitted.
Because they released it as open source purely to lure people in and get them using it enough so that switching away would be difficult for them. If they're up-front with people and mention that it'll be open source up until a time of their choosing, after which subsequent versions will be proprietary, then I don't see a problem and no-one's getting tricked. When I'm choosing an open source tool to use, then I want t…
Any open source code that requires constant maintenance either has FAANG support or would switch license in the future. I don't think that donation or pay for support could pay market rate to talented developers except in a rarest of rare case(e.g. sqlite which has very high user to developer ratio). Just treat not open source product differently than open source. Assume that the current version is all you are gettin…
One of the advantages of using open source code is that updates aren't purely done for commercial reasons and popular projects will tend to get a lot more people working on them than a similar proprietary piece of code. There's a lot to be said for enthusiasts working to make something better because they want to, rather than a paid developer just adding in features that a sales team think will look good in publicity materials and not being permitted to spend time fixing long standing issues with the code base.
It's an implied social contract between the developers and the users - the users will often recommend the software to others and there's an expectation that a popular, active project (i.e. not just some code that someone's published and then left alone) will continue to be active.
Switching licenses is only really feasible where all the code is owned by an individual (person or business) - certainly switching Linux to a different a license would be incredibly difficult.
It's all about getting people to work together rather than in competition.