Bitrix24 Open Source -

However, Bitrix24 offers a edition. This version provides users with the PHP source code , allowing for extensive customization. While you must pay for a license, the ability to modify the code makes it a "functional" open-source alternative for many businesses. Why Businesses Look for "Open Source" Bitrix24

If your license expires, the software continues to run (no kill switch), but you lose access to updates and official support. This is the trade-off: Freedom to modify, obligation to pay for IP. bitrix24 open source