I am very interested in the following ARM Cortex-M0 microcontroller:
http://www.nxp.com/products/microcontrollers/cortex_m0_m0/lpc1100/LPC11U24FBD48.html#overview
However I'm turned off at the thought of having to license their development software, which I found here: http://www.lpcware.com/lpcxpresso
Do I have options? My goal is to PCB design a custom development board based off of this microcontroller or similar (Cortex-M0/M3), and be able to program it via (micro) USB. Frankly I'd rather write ARM assembly - and likely be able to find good open source stuff to get me started - than have to use a proprietary IDE.
Thanks for any help; also open to alternatives based on my goals.