Another factor when qualifying "openness" is compatibility and platform lock-in. With Android, you're using a completely custom Google application environment. No X, no recognizable desktop toolkits. Hell, the Java isn't even quite right. In sum, that means that applications you program for Android only run on Android (VM porting doesn't really count here).

Maemo's advantage here comes with its compatibility with desktop Linux. It has X, it has GTK+ and Qt. Applications you program for Maemo are easy to run on other platforms (especially with Qt)—Linux, OS X, Windows, Symbian—and applications for these platforms (especially Linux GTK+/Qt stuff) are easily ported to Maemo.

Tools you recognize on an ecosystem that isn't designed to lock you in to a vendor's platform.