Thank you for using Userify!
One company account per actual company. Multiple companies are absolutely ok (for example, if you are providing consulting services to a client), as long as these companies are separate entities and not just as a way to circumvent the limit on 20 servers free.
You can sign up for Userify and use it on up to 20 servers free. Your account will show "Free tier" in the utilization section, and will also show a projected total, if you were to exceed the free tier. (Please be patient; these reports can take time to generate and may need to be re-run.) If you exceed 20 servers at any point through the month, then a bill will be due. (You can see an estimate of what it would be at any time.)
Because you don't need to provide a credit card for Userify to begin using it (or ever, if you stay below the free tier limits), then your service may be temporarily suspended at the end of the month if no billing information is on file and you've exceeded the free tier. As soon as you update your card after receiving the temporary suspension notice, your service will be promptly restored.
Thank you for abiding by these policies and for helping us to continue providing the world's best SSH key and user management software.