I would like to protect the videos on my site from being downloadable. Can I accomplish this through generatepress? If not, is there a free or inexpensive alternative you would recommend?
this is not a GeneratePress thing. You would need to look at paid services.
Vimeo Pro allows you to restrict content access to defined sites and to only those who a shared link is provided.
Amazon S3 & CloudFront provide a fully encrypted service that would restrict download.