Is wireframe.cc the perfect indie hack?

Yesterday I discovered wireframe.cc - a beautifully executed web app for making wireframe mockups. I've been researching and it appears to have been released in 2012, well before this community existed. Yet it seems to espouse some of the ideals of Indie Hackers of simple well executed SaaS. There is a Twitter marketing account but they haven't had to use it much as it looks like the Product Hunt went well and it was picked up by a bunch of press outlets after that. I guess it must be making some profit because it is still around 7 years later.

There is so much I love about this:

• You can use it without signing in.
• The interface is minimal and focused.
• It's a single-page web app.
• It appears to have an un-fancy PHP backend.
• The pricing model is clear and simple.
• The signup and payment flow is straightforward.

Does anybody know anything about this site and who created it? This is the exact kind of stuff I aspire to build. I really want to know if they bootstrapped and how they built it and how the model is working for them.