Hello,
From what I understand, Oviyam is inherently bound to DCM4CHEE, and cannot currently work in a standalone mode with other DICOM servers.
However, this forum is not about Oviyam: Please instead get in touch with the developers of this project.
As far as Orthanc is concerned, the Orthanc Book contains a list of alternatives to Oviyam:
Regards,
Sébastien-