While more donations and contributors are always welcome, the thing open source projects really need to break through are project leaders and UX designers to polish the software to make it more appealing.

Blender has come a long way in recent years by concentrating on these. There are also excellent videos by Tantacrul about his work on Musescore and Audacity after he made a video about Musescore and they got in touch with him to fix the problems he brought up.