In general, it can be relatively involved, which is why we have the repo so that when developers have done it once they can publish their binaries and we can all use them. The only video editing tool I can find is
this mpeg tool which is a bit limited in these days of vp9 and theora codecs.
If you can find the source for something, you can compile a hell of a lot using
code::blocks (or there are ways to cross compile), but these all depend on having the source to whatever you're wanting to run. You might also be able to nick some debian softfp binaries that should work too, I assume, but I don't know what would fit in 512MB of RAM to be honest. I personally think if you want to do video editing, you need a Pyra or a laptop. On my server where I generally transcode videos I've downloaded for smaller screened devices, I upgraded the RAM from 2GB to 4GB just for that, so even using ffmpeg on the command line I expect to be fairly painful.