I am not sure if the article suggests J-1 for people who are studying abroad, or for international students studying in the US. For international students studying in the US, I would highly recommend being on a F-1 visa instead of a J-1 visa and then applying for a CPT (or OPT if you are done with college) for an internship. J-1 has a requirement of working for two years in your home country after graduation. If you plan to continue working for the startup after graduation, this 2 year requirement could become a big issue (you need to apply for a J-1 waiver and do quite some paperwork to get rid of it).

In general, for international students studying in the US who want to start companies or work at an early stage startup in the US, I would recommend reading up the CPT and OPT rules. Those can be very useful in the early days until you have sufficient funding to move to a visa category like H-1B that has a minimum salary requirement.