Is Vibran an all atomic normal mode analysis?
*** Yes (it uses the force field you read), but there are also ways of coarse-graining the NMA.
Is it analytical or numerical?
Is it just in the basis of Charmm Forcefields?
*** No, any force field can be used, and there are also ways of coarse-graining the NMA.
Can this module obtain and report the eigenvectors or just can report the amount of frequencies?
*** Eigenvectors are available and can be reported.
Please read vibran.doc and formulate more precise questions.