Free software Flash replacements and the JavaScript trap
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.
The JavaScript trap
Even if we had a complete and free SWF implementation, it would interpret nonfree programs that websites publish. It is exactly the same problem as the JavaScript trap: using free software interpreters to run untrusted nonfree software from the Web. (I haven’t noticed this issue before reading the RMS’s essay on JavaScript and gNewSense’s page on SWF.)
Some sites like YouTube are moving to providing videos via the HTML5 video tag. It doesn’t solve this problem, since now nonfree JavaScript programs serve the same purpose as previously SWF. I think it might make writing free software replacements easier, due to free development and debugging tools available for JavaScript.
Why we need video downloader programs
Issues with specific video publishing sites are completely solved for their viewers by not running the code that the site provides (either SWF or JavaScript) and using a free software program to obtain the video. This can be done by youtube-dl, a command-line program; UnPlug, a browser extension; and many other programs. There are also extensions that display the video inline on the page without using its builtin player.
These tools support only specific sites, while very many are supported by youtube-dl despite its name. On other sites you can usually find the video URL by reading the source of the HTML page or the included JavaScript code. (It might be a nice fetish to have.) I don’t know what work is needed to use an unsupported site with a free SWF interpreter like Gnash.
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.
(While I highly disagree with completely rejecting JavaScript due to its usefulness in free Web applications, the arguments used against it clearly apply to SWF. Video downloader programs and browser extensions are software that we can write to replace nonfree software provided by websites.)
Flash animations
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.
JavaScript and HTML5 canvas are replacing this use of Flash too, so now nonfree programs using better tools control the animation.
Publishing your own works
If you write an interactive website, use JavaScript. Release your code as free software. If you make videos, release them on your site using a free software-friendly video format like WebM, or use Web applications like GNU MediaGoblin (possibly an instance run by your friend).
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.)