Sure, that is a useful condition and is a no brainer to add if you need leverage copyright anyway.

But would it be enough to spur the open source movement on its own if you could legally decompile all binaries and redistribute that? Probably not.

Its not like source vs. binary is a clear distinction - between code obfuscation, generated code, transpilation, etc. there is a lot of wiggle room what should or should not be OK.

The GPL makes it a pretty clear distinction, "preferred form for modification" is pretty clear, but decided on a case-by-case basis. Obfuscated code is not source, generated code is not source, transpilation is often not source but could be depending on how you use it afterwards, bitmap images are often not source but they can be, executables are usually not source but could be, videos are not source but could be. Some links discussing what source is here:

https://www.inventati.org/frx/essays/softfrdm/whatissource.h... https://b.mtjm.eu/source-code-data-fonts-free-distros.html https://wiki.freedesktop.org/www/Games/Upstream/#source https://compliance.guide/pristine https://opengameart.org/forumtopic/source-required-for-art-l... https://wiki.debian.org/rly-free-software