Open source Not […] allow […] commercial applications
For some definitions of open source, this is contradictory (FOSS). Some non FOSS licenses do limit commercial use while making the source available, this could be a possibility for you.
But, I’d instead recommend that you check if a copyleft license such as the GPL provide enough protections for your use case.
I don’t have the information regarding xmodmap, but here are two other options which I am using if you are interested.
With the compose key set, you can hit / = to get ≠. Or you can set custom sequences in .XCompose, but I don’t believe you can get the exact combination you suggested.
There are other ways to structure and edit programs than just a bunch of source files that we manually edit through a text editor. For instance image files as in Smalltalk. I don’t see any reason why a visual representation couldn’t succeed in this regard. The issue, imo, is that text is really nice to work with, and it would require a very nice visual editing experience to beat the text based tools we have today.