The wording "If this kickstarter is funded, we are going to make a software product [...]" sounds like you haven't even started making it yet, which is immensely discouraging to potential backers. Maybe change it to "we are going to release" or "we will be able to finish" or something similar?

With a lot of fairly basic features locked away behind a paywall (Pro), this seems rather unappealing to me. I dig the concept of an online image editor with seamless uploads to Imgur and the like, but paying ~$5 for what is essentially the ability to use the equivalent of a free app (most of the Pro features are available in free image editors) without having to install it just doesn't seem right to me. I'm all for a Pro version, but I think in its current form, it just hobbles the basic editor to the point of nigh uselessness. I'd love to see some of the Pro features moved into the Basic version, and other features added to Pro. I think keeping animation-related features in Pro and "productivity" features like multiple views is a fine idea, but having to pay for things like layers, transparency, smudge, and indexed palettes will just drive away the people who should be your core users. Monetize the social aspects (storage, featured posts, etc), not basic features.

The tutorial is about thinking in terms of tufts and layers of fur rather than single strands. Although some furry animals, especially young ones, are nondescript fuzzballs, most have distinct tufts or even layers of tufts that their fur clumps into. For example, check out the lines on the neck and chest of this bear, and on the abdomen of this one. By stylising these clumps, you can get fur that reads well, communicates the form, and looks awesome. Although normally I recommend looking at the real thing over artists' renditions, in this case other art might help you see this clumping more clearly, since some animal artists have it down to a science. Here, for example, check out how the artist has used both layers and tufts on the back of the front legs, while keeping some parts smooth, which gives a sense of varying, flowing fur. Some(1) more(2) inspiration(3). These are all paintings so they have room to add more detail, but the basic idea of clumping carries over to pixel art fairly well.

You should check out this thread here on Pixelation, it deals with pixelling fur in a couple of different ways, at a size comparable to yours. Clumping is very helpful to keep in mind when deciding where to place the shadows/texture that creates the fur.

It still essentially has an outline because of how heavy-handed your AA is. An outline-less drawing is one that uses boundaries between light and shadow and boundaries between colours to establish its forms and shapes, but you're still relying a lot on lines.

To make the lineless look work, you have to double down on the forms. In my opinion, a good sense of form is what was missing in the original anyway :]

- The neck appears to widen towards the bottom, like a section of a very long cone. Necks are a bit more complicated than that, it's more that the back widens (because of the trapezius muscle connecting the neck to the back and shoulders), and the front narrows. You could create this complex shape with the shadow. Just how much you show depends on how realistic you want the image to be. If you're going for a simplified, stylised look, then you should just show the neck not getting wider; you only need to bother with details like all the bits that stick out of necks in the front if you want a realistic neck. Because you're drawing it like a cone, the shirt also doesn't appear to rest on the neck and shoulders, it appears to intersect/clip through them instead. Try having the shirt go up a little at the back to look like it's going over the trapezius muscle.
- The hair casts a massive shadow over the forehead, but doesn't seem like it's meant to actually hang over the forehead all that much. This inconsistency looks strange. If it doesn't overhang the forehead, then just removing that huge shadow should be all you need. If it does, then you need to show that with the shadows on the hair.

Here is a paintover with the above implemented and the remaining outlines mostly removed:

The overly detailed neck is just to give you an idea of what's there. That level of detail is too much for the rest of the image, I think it looks better simplified. However, note that even in the simplified version, I left some hints of the "dips" at the edges of the shadows and where the shirt overlaps it, so it still feels detailed without the detail being drawn.

I also made a number of smaller changes all over the image to give it a little more definition, and made the skin shadow colours a little warmer. Hopefully this'll give you some ideas to improve your portrait!

I think if the hairline wasn't perfectly horizontal, it would look a little better. Also, isn't the Donald's hair more orange than yellow?

Is it just pixel art or all kinds of art?