I don't know of any way to pay to watch it on-line directly. I guess to support the producers at this moment you'd have to order the DVD. I have an impression that the film can still be found on-line with the search engines, some place where some user posted it on some video platform and it's still not removed, but I haven't actually tried.
Yes, somebody should also suggest to the producers to make the film available for on-line purchases (I'm too lazy to be that somebody this time).
You can read the DVD reviews on amazon.com to get the idea how people respond to it. Amazon sells the DVD cheaper than the official site.
I greatly admire Ellsberg's courage and moral consistency.