1. Overconfident forks that die out
“One that doesn’t seem to be listed is ‘overconfident fork’ in which someone forks an existing project out of anger or hubris, but that fork never gains critical mass and eventually withers away.” — tomwheeler
2. Hostile maintainer behavior and lack of stewardship
“If you are going to leave a project as leader, either see if someone else wants to take over or leave a note that the project isn’t being updated.” — HerbManic
3. Burnout & the need for responsible sunsetting
“code was open‑sourced with every intention of becoming a thriving community‑driven project, but in practice users only take from the code what they want… Eventually, the maintainer decides that they have better things to do… the project gradually gets abandoned.” — ndepoel