One of the nonfree programs that make it hard for many people to use completely free software operating systems is Adobe Flash. There are several free software projects aiming to replace the Flash interpreter, one of them used to be an FSF high priority project. I don’t believe that developing such programs will significantly help people stop using nonfree software. (While hardware compatibility issues resulting from free drivers requiring nonfree firmware are well-known and probably more noticeable, they can be easily avoided by buying appropriate hardware, it’s not hard. There are social issues that make people use the same websites as their friends, but not the same computer hardware.)
While Flash has many uses, both as a Web browser plugin and for desktop applications, I will focus on its common use for video players on websites like YouTube.
Replacing Flash is hard
No free software implementation of SWF, the file format used by Flash, can currently support most such files used on the Web. gNewSense contributors mentioned both patents and incomplete specifications making this hard to do. Another issue is the Digital Restriction Management implemented in Flash. A sufficiently complete free implementation would probably violate anti-circumvention laws making DRM an effective restriction of our freedom.
Why we need video downloader programs
Being able to download the video and save it on persistent storage (instead of downloading it just to display it in the player) is needed for at least several useful reasons: we cannot remix without downloading the video, we cannot protect against centralization and copyright censorship while accessing the works from a single centralized site and we cannot share it with our friends (or be a good friend to them) without having a copy. Even the very limited freedoms weakly protected by copyright law as fair use cannot be used without storing a copy of the work.
Before Web videos became popular, SWF was often used for vector animations. This might include them in the difficult to reason about area between software and non-functional cultural works, while there is a simple reason to consider it software: it has antifeatures. We need the freedom of free software for such works to make them respect their users.
Publishing your own works
To prevent DRMed sites from using your videos to restrict their users, use a free culture license that disallows using ‘effective’ technical restrictions of the freedoms that it protects, like CC-BY-SA 4.0. (YouTube requires giving them a different license, don’t upload your work there.)