Limit their outgoing connections until they provide a CC number. Most software can be initially tested without needing to connect to the wider internet. Throw in plenty of /examples directories for the different applications you offer.
You could provide some approved outgoing connections to trusted plugin/package repos.
If you want to get stricter only allow incoming connections from the trial user's IP to stop them hosting scam landing pages.
You could provide some approved outgoing connections to trusted plugin/package repos.
If you want to get stricter only allow incoming connections from the trial user's IP to stop them hosting scam landing pages.