Bitrix24 Cloud version is SaaS, it is rented by our users. It is deployed, hosted and maintained by Bitrix Inc. in the Cloud. You can use your Bitrix24 account with a free subscription, or with a paid plan. Please see our plans and tariffs page.
Bitrix24 on-premise (self-hosted) version is licensed on "per-user basis". If you need more users than your license key provides, you can purchase On-Premise Edition Upgrades. Bitrix24 On-Premise is fully customizable (color schemes, layout, menu items, header, footer, etc.) and provided with the full source code. It can be deployed and hosted by the end-user or by Bitrix Partners.