What is ASIO4ALL? Most DAW's require the use of an ASIO driver which helps your computer communicate with connected audio devices correctly and provide low latency recording,. ASIO Drivers will bridge the gap between your computer's sound card and your DAW.
Is ASIO4All any good?
It's a great tool. And as for any tool, you need to understand what it's designed for. If you use a hammer to make a soup, you won't have great results (okay, the analogy is shakey, but you get the idea). ASIO4All is perfect if all you need is playback from the DAW, but you don't have an audio interface connected.
Is ASIO free?
Asio4All is a free, hardware-independent, low-latency universal Asio driver for WDM-supported devices and software.
Is ASIO4All open source?
Other free or open source alternatives are ASIO4All, FlexASIO, ASIO2KS, and ASIO2WASAPI. Being a proprietary protocol, it does not have any universal compatibility with Windows-based DAW and other recording software.