If you're a beginner and would like to use 32-bit MCU, I'd recommend ARM Cortex-M microcontrollers. A lot of documentation, sample code, manufacturers etc. Atmel (that is a part of Microchip now) has its Cortex-M series (xplain boards), STM32 is also good (Discovery boards, NUCLEO are perfect to start).
As for licensing, vendors usually provide low-level libraries with small restrictions, like ASF for Atmel, HAL for ST (save licence in the source, use the code only with vendor MCU etc), so it's not a problem.