Hi,
CCSv4 and newer do not have any limitation for any toolchain used to build ARM code, being either TI or GCC.
References:
CCSv4 and v5: http://processors.wiki.ti.com/index.php/Licensing_-_CCS#Free_Licenses
CCSv6: http://processors.wiki.ti.com/index.php/Licensing_-_CCSv6#Free_Licenses
Regards,
Rafael