I started looking into developing APEX multilanguage applications a while ago. Although the premises looked good (APEX has globalization features and allows publishing an application in multiple language), the case at that time, which involved publishing a bi-lingual application in a runtime environment proved to have major faults. Still, this whitepaper describes the complete process or developing and publishing an APEX multilanguage application.
The main unanswered question remains: is there a way to publish multilanguage applications in an APEX runtime environment, where each deploy is done by running sql scripts with no Application Builder access? Anxiously waiting for an answer for 2 years!
Download the whitepaper from here.