Sakai does not as yet support the JSR 168 portlet standard and is, at version 1.5 starting to add WSRP support. The TPP can be used as the template for constructing and subsequently sharing Sakai tools. A wise strategy at this point would be to code the minimum of tool logic in the Sakai TPP specific part of the tool and factor out the main logic into delegates, ready for a recoding of the tools into the JSR 168 standard. On the other hand, the TPP offers up a lot more functionality from the framework than seems to be the case with JSR 168. You can use Hibernate to create a database structure required by your tool, for example.