First, I don't think that "enabling sight" is the right term to use here. It's just making a certain device usable to the blind.
And yes, there are open source and free options available. iOS' accessibility APIs are closed to third parties and VoiceOver is the only option on that platform. However, there is free and open source screen reading software for Windows, Linux and Android.
I can't say what the state of Orca, the free Linux screen reader, is these days, but I know development is still going on. Orca wasn't so much of a problem in the past when I tried it, it was more that it could be a real pain to get everything working together. Think reasonable low-latency sound output for speech, driving a braille display through the BRLTTY software, getting the screenreader runnign at the login screen etc etc. I hope that has improved by now, but I only interact with Linux through SSH sessions or local text console these days.
Then there is NVDA for Windows. A free and open source screenreader mainly developed by two blind guys. On many fronts it has feature parity with the very expensive commercial offerings and even surpasses the commercial offerings on certain points. I use it as my daily driver.
In the past I also used a Mac near fulltime, but the VoiceOver of Mac OS became to buggy for my professional work. Also, usually updates only came when the OS was updated, so fixes and new features could take a while. So, long story short, open screenreader on a closed operating system that provides stable APIs seems to be the best of both worlds for now.
And yes, there are open source and free options available. iOS' accessibility APIs are closed to third parties and VoiceOver is the only option on that platform. However, there is free and open source screen reading software for Windows, Linux and Android.
I can't say what the state of Orca, the free Linux screen reader, is these days, but I know development is still going on. Orca wasn't so much of a problem in the past when I tried it, it was more that it could be a real pain to get everything working together. Think reasonable low-latency sound output for speech, driving a braille display through the BRLTTY software, getting the screenreader runnign at the login screen etc etc. I hope that has improved by now, but I only interact with Linux through SSH sessions or local text console these days.
Then there is NVDA for Windows. A free and open source screenreader mainly developed by two blind guys. On many fronts it has feature parity with the very expensive commercial offerings and even surpasses the commercial offerings on certain points. I use it as my daily driver.
In the past I also used a Mac near fulltime, but the VoiceOver of Mac OS became to buggy for my professional work. Also, usually updates only came when the OS was updated, so fixes and new features could take a while. So, long story short, open screenreader on a closed operating system that provides stable APIs seems to be the best of both worlds for now.