IANAL either, but I think, if someone were to take it to court, it would:
1) Travis achieved a market-dominant position in part thanks to widespread use by open source projects.
2) Open source projects invested significant resources into integrating with Travis based on their promise.
3) Moving to something else would take significant resources. The exact loses are probably exactly how much it would cost to pay to continue to use Travis (and collecting some of that money is precisely why Travis stopped offering a free service). If it wasn't significant, Travis wouldn't have made the change.
That doesn't mean it's worth anyone's time to litigate.
As a footnote, the traditional way to handle something like this is to continue to provide a free service, but to make it worse and worse and worse. Travis could satisfice the promise by keeping an insecure Raspberry Pi under someone's desk running old code as the "server farm" for open source. Courts don't necessarily consider satisificing to be following through on a promise, but costs of litigation go way up when there are open legal questions like that. At that point, it's usually almost definitely not worth anyone's time to litigate.
1) Travis achieved a market-dominant position in part thanks to widespread use by open source projects.
2) Open source projects invested significant resources into integrating with Travis based on their promise.
3) Moving to something else would take significant resources. The exact loses are probably exactly how much it would cost to pay to continue to use Travis (and collecting some of that money is precisely why Travis stopped offering a free service). If it wasn't significant, Travis wouldn't have made the change.
That doesn't mean it's worth anyone's time to litigate.
As a footnote, the traditional way to handle something like this is to continue to provide a free service, but to make it worse and worse and worse. Travis could satisfice the promise by keeping an insecure Raspberry Pi under someone's desk running old code as the "server farm" for open source. Courts don't necessarily consider satisificing to be following through on a promise, but costs of litigation go way up when there are open legal questions like that. At that point, it's usually almost definitely not worth anyone's time to litigate.