Publish in the academic journal, then follow up with a second publication in an open source journal. You have two different platforms with different goals. They also have different audiences.

The good news is that you seem to be doing good recognizable work. So focus on that. The academic paper will help you get some recognition and more importantly diffuse your ideas in the academic community. The open source journal may be helpful for a wider audience who finds your code on git hub, by helping explain a little more than the typical read me , and by writing it you may fill in some gaps in your current explanations and implementation and help gain a wider audience for your code.

Publishing takes time, but I have found that 5 or 10 years later I like having a paper I can go back to, or if I have to explain something to people, I can pull out an old paper. I also find that it helps me remember what I was thinking about at the time.