One software license is required per workstation.

There are 2 kind of licenses for Mootools software.

Perpetual License
The Perpetual license is a license to use the software valid for life. This license does not expire and includes 1 year of free upgrades.
The perpetual license entitles you to free updates to your software for 1 year from the date of purchase. This includes upgrade to major updates or to higher versions.

What happens when the free upgrade period is over?
You can continue to use your license for life or renew your license to a newer version with an advantageous price. You will then benefit from a new perpetual license which again entitles you to 1 year of free updates.

Subscription License
The license by subscription is a license valid for 1 year from the date of acquisition.
This license gives you the right to update the software during this entire period, including major upgrades or to higher versions.

To continue to use the software you will need to renew the Subscription License.