While the FSF discourages use of the Android marketplace, they do say there's no specific GPL conflict. Compliance is potentially a bit more of a pain for the developer, of course; strictly speaking they have to make sure the LGPL-covered code is available for download for three years after distribution ends. They also strictly speaking have to provide a mechanism to re-assemble the app; example here: http://sparrowmailapp.com/lgpl.php (though note that a lot of people just don't bother).