Although Formspider uses static URLs for Apps and you cannot modify Formspider URLs from inside Formspider, URLs can be altered from your middle tier configuration.
To rewrite URLs, there are various options.
First option is to use an Apache httpd server in front of your application server (servlet container). With Apache httpd, you can use Apache mods mod_rewrite and/or mod_proxy to change URLs. Using mod_rewrite causes the modified URL to be visible to the end user. However, when you choose mod_proxy, the modified of URL will be invisible to end user. For more information, you can visit Apache httpd documentation on mod_proxy and mod_rewrite.
As a second option, you can use Tuckey's URL filter.(http://tuckey.org/urlrewrite) This is virtually the same thing as the Apache's mod_rewrite. The difference is that it's implemented in Java to make it available to Java-based application servers.
As a third option, if you use glassfish as an application server, you can take advantage of its simple URL rewrite mechanism. You can find more information for this option from http://serverfault.com/questions/169643/how-can-i-rewrite-redirect-urls-in-glassfish-v3.