What, if any, are the risks when migrating from Apache JServ to jakarta-tomcat? How many changes will have to be made to existing (JSDK2.0) java servlet code?
There are always inherent risks when moving from one platform to another, but jakarta-tomcat is rather stable with version 3.2 expected out first week in September 2000. This should have as much stability as Apache JServ has built up.
Servlet 2.0 code should run just fine in a Servlet 2.2 compliant container as the API is backwards compatible. However, as the API is more now better defined, your servlets might be using "incorrect" servlet API behavior. Look for getPathInfo(), getRequestURI(), and getServletPath() as you might have to change how code that calls these methods.