We are pleased to announce that the CMSIS software components used by the mbed SDK have been released under a permissive BSD open source license!

After we announced the open sourcing of the mbed SDK a couple of months ago, we received many queries about the license of the CMSIS components used by the mbed SDK.

The CMSIS package from ARM is not a typical "software project", it is the vehicle used by ARM to provide standard software interfaces to the Cortex-M processors. For this reason ARM adopted a customized license to serve its standardization effort. Unfortunately, not being a well-known license, many developers struggled to understand what were the implications of mixing the actual CMSIS software components with proprietary code, or code released under a different open source license.

To clear this confusion, ARM has officially released the software components of the CMSIS package, used by the mbed SDK, under the well known and understood BSD license, while the CMSIS Specification itself remains licensed under an ARM proprietary licence.

In the official CMSIS package, this is the relevant content of the "CMSIS END USER LICENCE AGREEMENT.pdf":

The package also includes the components contained in the following directories:
(a) ./CMSIS/DSP_Lib - DSP Library sources and examples;
(b) ./CMSIS/Include - Header files;
(c) ./CMSIS/Lib - DSP Library build for various toolchains;
(d) ./CMSIS/RTOS - Header file template for CMSIS-RTOS implementation; and
(e) ./Device - Template files and implementations for Cortex-M class processors.

All of the above components are licensed to you under the terms of the BSD licence, which is incorporated within
or alongside the above components.

This makes the whole mbed SDK completely open source with a mix of well known and understood permissive open source licenses: Apache and BSD.

Have fun and keep innovating!