IMO these myths are mostly true and are a major fact why OpenSource doesn't work as it could/should. From my own experience it's difficult to avoid running into the same traps. Usually it's much easier to fix something in building a workaround instead of fixing the problem at the right place. Sometimes it's not even possible to do it right because of political reasons but mostly it's because we are just too lazy or "don't" have the time.
Fortunately since in OpenSource problems _can_ be solved at the right place it will be done sooner or later. Therefore OpenSource is still superiour to ClosedSource but the process is much slower than it could/should be.
See "http://wxguide.sourceforge.net/" for ideas how to design your app.