Jaybird is licensed under LGPL. Current releases of Jaybird do not explitly specify an LPGL version. This means that you can choose which version applies. Future versions of Jaybird may specify an explicit version, or be released under a different license.
Since there is no clear answer on the question whether compiling Java code that uses interfaces is static or dynamic linking, the following clarification is needed:
javax.resource.*packages, from the authors point of view this is dynamic linking and an application that uses Jaybird in no way is infected by the LGPL license.
In other words - Jaybird is free for use in commercial and non-commercial applications as long as it is not modified with limitation to the license. If a person or company modifies Jaybird, changes these must be published under the LGPL license.