Thought I'd chime in here. I'm a Front-End developer student and started teaching myself GIMP as a way to adjunct my studies. About six months ago I found myself having a drink without a professional Front-End developer and I asked him if these sorts of programs come in handy. What he told me was this-
- Almost all the front-end developers at his workplace have some experience with image editing. For a few employees, they work more on the raster editing side then the coding side.
- The majority of Front-End developers use OSX with Linux a close second.
- The OS X users were slowly moving away from Adobe because of the cloud license
- Some OS X users were using GIMP. Most were using "this new program, Affinity Photo." This, I should mention, is how I heard about Affinity, and now I am a paying customer
- The Linux developers were all using GIMP
- Almost no one uses Windows
I think a point worth mentioning is Linux is a mostly untapped market. The biggest competitor, Adobe, is a non-player. The current market share for Linux OS is estimated to be about 2.5%. That's not huge, but worth considering is that's 2.5% of a market with no commercial competition. I other words, Linux users- as opposed to OSX and Windows users- will more naturally gravitate towards Affinity. Affinity users, in turn, will also be more willing to consider Linux.
EDIT: Also, it's worth considering the value of word of mouth. For example the developer I spoke to used OS X. I don't and I never will. I personally find it cumbersome and use a dual boot Linux/Win environment. If a piece of software is OS X only that means I don't use that software. When Affinity came to Windows, that didn't matter. He recommended it, I trusted his opinion, and gave it a shot. And PAID for it. In other words, those Linux users will be another avenue to promote your product, and potentially increase sales in not just Linux, but also OSX and Windows. I love the idea of a kickstarter.