This article reads as though it is seen m0n0wall as a failure, or that it demonstrates a weakness in the way that open source software is developed.
Yes, the project is closing but it is clear that so many people and other software packages owe so much to m0n0. It's code base is old and had been superceded in terms of flexibility and maintainability by those who came later and built and modified what was there . And so, in time, these packages will be replaced by others building upon them.
It's not a failure, pfSense and the others are all the children of M0n0. It has gone into retirement but it's offspring have great futures ahead of them.