Well you can create videos with ffmpeg, however I don't know any lib in which you can do this programmatically.

What do you mean with creating videos? Which kind of videos?

You mean something like voucherify.io ?

+1 for graph.cool
it is really awesome

sounds cool!

If you mean css bugs here in WIP, I think you can dm @marckohlbrugge ;)

Well,
it will be really hard to sell it without a community.
I would suggest that you make a few free videos oder even free micro courses to build up a community.

And then sell the main course.

You mean programatically? After Effects / Premiere can do this.
However, ffmpeg should be fine.

What are your settings? You can set the output quality with

-qscale:v 2 The range you can set is 2-31 I think while 31 is the worst quality.

There are also a lot of plugins for ffmpeg so you can output tiffs, of jpegls for lossless jpgs

I guess the common way is gem your stuff.
However it involves a lot of work.

Git submodules could be a way to go, however I would not recommend them. Used them once and its a real pain.

I think it is super annoying if you sign up for a free account and it is not clear that there is a paid tier, too and then you see that you have to pay.

Say it upfront and do not annoy your users.