The OpenAI Startup Fund, a venture fund related to — but technically separate from — OpenAI that invests in early-stage, typically AI-related companies across education, law and the sciences, has quietly closed a $15 million tranche. According to a filing with the U.S. Securities and Exchange Commission, two unnamed investors contributed the $15 million in new cash on or around April 19. The paperwork was submitted on April 25, and mentions Ian Hathaway, the OpenAI Startup Fund’s manager and sole partner. The capital was transferred to a legal entity called a special purpose vehicle, or SPV, associated with the OpenAI Startup Fund: OpenAI Startup Fund SPV II, L.P. SPVs allow multiple investors to pool their resources and make an investment in a single company or fund. In the VC sector, they’re sometimes used to invest in startups that don’t fit a fund’s strategy or that fall outside a fund’s terms. SPVs can also be marketed to a wider range of non-institutional investors. It’s the second such time the OpenAI Startup Fund has raised capital through …