I'm the author of the RGraph library. I've been in the IT industry for over 22 years and programming websites for about 20 of those.
I started out doing tech support and then moved into the emerging world of Web Development.
In terms of financial benefit from RGraph - I get the odd donation from RGraph - and you can see how many I get here: https://www.rgraph.net/donate.html
Most years I get less than £250 from it - which doesn't cover my hosting costs and the costs in running the website.
RGraph isn't a business, when I initially started it back in 2008 that was certainly the intention. though poor SEO performance has eliminated that idea! It's currently MIT licensed - and therefore entirely free. Oh and that's the way it's staying.