OmniForm was previously developed by Nuance, but they discontinued support for this application and focused on a different category. It's impossible right now to obtain an activation code since they don't actually have the product and the activation servers anymore.
The best thing right now is to choose an alternative, and luckily there are some available. For example, you could try FormDocs. They even state it can be used as a successful alternative to OmniForm.
