It depends what model RTV you have. The newer models, which have an Ethernet connector, require connecting and activing even to be used as a manual VCR-like. They no longer enforce subscriptions, so that shouldn't be a problem. However, you will likely need a remote just to go through the setup to configure the unit.
FYI, many multi-function remotes can run enough of a ReplayTV for you to be able to set them up. Check if you have any multi-function remotes and say that they support DVRs or PVRs models Panasonic, SonicBlue, or ReplayTV. Or, pick up a cheap multi-function remote from Walmart that can run it. Even Cable Box remotes can often control a ReplayTV.