We have developed OpportunisticOwnCloud to target Android SDK 17 (Jelly Bean). The minimum requirement is Android SDK 8 (Froyo). We have run OOC successfully on systems running Froyo and Gingerbread.
While OOC should be able to interface with any WebDAV server using the Sardine library, we recommend installing and running an ownCloud server instance to use with OOC. See <http://owncloud.org/install/>.
DEVELOPERS ONLY
In order to contribute to OOC, you must have Android ADT. We recommend downloading it from http://developer.android.com/sdk/index.html as this provides the entire Android SDK, including Eclipse with ADT plugins.