Obligation to maintain?
The idea of freely sharing code is as old as computing. The first computer user group (SHARE, which originally was exclusively for the IBM 704) began in 1955 and defined a card-based format for sharing software amongst the participating organisations as well as essential standards (such as linkage conventions) to make them readily reusable. Software from computer manufacturers was usually free as the computers were a hard sell without it and unless you'd bought a machine there was no way of making use of it. Copyright in computer programs wasn't really a consideration until there was a level of compatibility between computers - software was typically distributed either as assembly code or compiled object code - and the bundling of hardware and software came to be seen as anti-competitive. However, once people had to pay for software, they expected it to be maintained in a working condition in the same way as the computer itself.
The twist that the Open Source movement put on this was to make the source code freely available on request, but having thereby eliminated any commercial element from the creation of software nevertheless offered ongoing support and maintenance as a possible source of income.
We now seem to be in a situation where even that source of income has been eliminated, not by any particular law or campaign, but simply by developers capitulating to peer pressure. And having done that, they're of course finding themselves expected to serve up not only support, but also functional enhancements they don't themselves need, free of charge.
It's not only unsustainable, it's also counter-productive. It leads to developers and maintainers simply walking away and leaving projects abandoned. It also leads to the constant churn of new frameworks and re-implementations because developers prefer to move on to new things. And of course it leads to a worldwide distributed security threat because, outside a few prominent projects, no-one knows who's actually writing the code or cares what's actually in it (despite, ironically, the source being open).
If a solicitor prepares your will, you don't expect to get free updates for life. If a plumber fixes your tap, you don't expect them to come back at no cost whenever it drips in future. I'm all for developers freely sharing their code, but that altruism should not come at the cost of a future obligation: it's the recipient's job to decide whether it's useful, how to adapt it to their environment and to maintain it. That might involve paying someone (possibly the original author), but no-one should expect a free ride.