5
WSRP is one year old an not widely supported.
The "Big Boys" like Red Hat Portal server, IBM WebSphere, BEA something or other are interested in this kind thing... That does not mean it can't apply to Xoops, but most of those are Java and huge.
I do not think it is relevent anyways as no one is using it, even those listed above. They all favor JSR 168 as they are Java.
As for "wrapping the app in xoops". This is easy with an I-FRAME. I did this with a webmail app. However, as Mith pointed out, the heavy lifting will come to use XOOPS permissions within the app.
This situation would be better with LDAP assigning permissions for both XOOPS and XYZ app, but a real integration would still not be there. You would be working with the outside app in a non-xoops mangement system. This would not be a true module.
Hope this helps.
JMass