Any person who fails to register as a developer in violation of this part 4 commits a class 6 felony and shall be punished as provided in section 18-1.3-401, C.R.S. Any agreement or contract for the sale or lease of a subdivision or part thereof shall be voidable by the purchaser and unenforceable by the developer unless such developer was duly registered under the provisions of this part 4 when such agreement or contract was made.