If you assign an issue to yourself, you are making a commitment to the Zend Framework community to fix that issue in the 'fix for release'. In fact, you are reserving that issue so that only you will be working on it. If you'd like to try working on an issue without a commitment, watch it and work on it without assigning to yourself until you are sure you will be able to finish it.
If you have any questions about an issue, send an email to the corresponding list. Please try resolving your issue on the mailing list before contacting the component owner, unless the component owner has indicated otherwise.