SIG Software
I call "SIG software" or "SIG development" (as in "Special Interest Group") the practice of taking a piece of FOSS software and adding the functionalities you care about or have expertise in, and then leaving it at that.
You can see this phenomenon in frequently-complained-about software such as Audacity or GIMP. During their development history, competent programmers have bolted on niche (and sometimes even advanced) functionalities they cared about, crammed them in a menu with the rest of the pile, and just left them there without a design in mind. Blender was also like this, but it famously made a major recovery and gained that feeling of cohesion that converted many people into using it.