The DS-5 community edition use the GNU toochain license by GPL, Does the ARM open the DS-5 community edition source code?
Only parts of DS-5 are under GPL (the GCC toolchain). You can get the sources to them from https://silver.arm.com/browse/DS500 (registration required). Look for "DS-5 GPL Source". Eclipse and CDT (without the ARM extensions) is available from eclipse.org.