So you inadvertently signaled "I'm looking for funding" in VC-speak ;)
Agree 100% I just wanted to make sure your expectations were realistic based on the what you wrote. I hope the best for you!
The market may not be large enough and opportunity may not be as fast growing that VCs expect, still it may be possible to build a decent size business with SageMath.
> Have you taken any external funding for SageMath and SMC beyond grants?
For SageMath, all funding is via grants, and I have almost no such grants these days (I used to get grants in the early days). There's a grant in Europe called OpenDreamKit that provides substantial funding right now. There's also one new NSF grant that will provide some funding for free open source textbooks built with lots of example using Sage.
For SageMathCloud, I did a round of Angel investment about a year ago in order to "bootstrap" things, and hopefully give us the time we need to build the business to be profitable. The Angel investors are a small group of people I know from the mathematics world. Right now the company is not profitable, even with a small number of low-paid developers, so it's critical to have this money to make up for the slack until we have more customers.
We can and should do a lot more marketing when the time is right. I hope that time is very soon.