Complex sentence: In 2003, Gretsch entered a business agreement with Fender Musical Instruments Corporation (FMIC), under the terms that Fred Gretsch III would retain ownership while FMIC would handle most development, distribution and sales.
Split into simpler sentences: In 2003, Gretsch entered a business agreement with Fender Musical Instruments Corporation (FMIC). Under the terms of that agreement Fred Gretsch III would retain ownership while FMIC would handle most of the development, distribution and sales.