when I run my project from eclipse the console ask me, besides username and password, the license key, but I want to use it for free. How can I do?
there is a free version?
Please check what exactly you are running in Eclipse. According to your description it seems that your main class is the ObjectDB Activator (which is not needed for free users) rather than your main class or your web application.
ObjectDB - Fast Object Database for Java (JPA/JDO)