Accepting money through Xoom, cash2india, remit2india, WU should be for personal use only. That means, a person in some foreign country can send money back to india for personal use (eg. Family expenses etc). However use of these services for commercial purposes is illegal according to RBI FOREX terms and is clear violation under FEMA Act.
Yes, if you sell any kind of softwares, script, ebooks or other services etc through any means (exporting on media or through downloads) you are required by law to have an Import Export License. You can apply for one through the Directorate of Foreign Trade. Any money earned without this license is illegal and can put you in trouble when you file your tax returns.