According to the changelog, see:

https://github.com/marxoft/cutetube2...ttan/changelog

the latest version of cutetube2 for Harmattan is 0.5.1, the same as for the Maemo5 and Symbian versions.

As to why marxian has not published an installation file for cutetube2 version 0.5.1, maybe he has no working N9 to test it on. Someone could ask him if this indeed is the case.