Each Digium system requires an Active Software license during first purchase/setup and licensing (subscription) for each mailbox/endpoint you wish to set up. In our case since we purchased the software independently of the appliance our cost has been
AA80 (Hardware Appliance), T1/PRI Card, 20x Titanium Subscriptions, 20x Digium Handsets (D40, 50, or 70)
This would entitle you to the hardware, software and up to 10 mailboxes or handsets. If you added a 21st handset, you could not, until you purchase 1 more Titanium subscription (you cannot mix and match).
At the end of the year, your entitlements for software support and updates end, unless you purchase a renewal. The renewals must include a base-software license, plus one subscription-level item for each mailbox you’re renewing (in this case, it might be 21). The renewals give you access to support, software updates, bug fixes, etc. and the ability to use/add any additional mailboxes/handsets.
So, lets take this example…
At the end of the year, you’ve used 19 subscription seats, but you’ve purchased 21. Mid way through year two (assuming you initially only purchased one year), you wish to add a 20th handset. Thats fine. Even though support has expired, you can still add the handset/mailbox. But, if you have any issues with the software/setting up the phone/etc., you have no manufacturer support.
On the other hand, if you had used all 21 mailboxes during your first year, and mid-way through your second year (again, you only purchased a one year license), you wish to add a 22nd handset. Even if you purchased the hardware, you would not be able to, as you no longer have any free licenses to use. You could, if you choose, delete some unused mailboxes to get below the 21 count and then re-use them, but that scenario is generally unlikely. To ‘true up’ your system and add the 22nd handset, you’d need to purchase the base software upgrade license, plus any of the additional subscriptions you need, in this case +1.
They do offer multi-year discounts to make the subscription fees a little easier to manage, however, this can be difficult sometimes in rapidly changing environments, where you forecast 50 employees for 4 years, but grow to 60. That being said, the base-license renewal fee is extremely competitive, as are the renewal licenses, they’re less than 25% of the original 1st year cost.
Digium licensing is one of the least expense and least complicated licensing structures out there. Since all features are included, you don’t have to worry about any other “feature” license keys.