Bizspark doesn't exist anymore, it's a single program called Microsoft for Startups now, and it does allow you to apply directly: https://startups.microsoft.com/en-us/faq/

But it's only for those developing an "innovative, technical solution unique in the market with a B2B focus that will benefit from access to enterprise customers," according to that link. IIRC the old BizSpark didn't have as strict of a B2B focus.