On May 5, 1993, Sun Microsystems announced Windows Application Binary Interface (WABI), a product to run Windows software on Unix, and the Public Windows Interface (PWI) initiative, an effort to standardize a subset of the popular 16-bit Windows APIs.

In February 1994, the PWI Specification Committee sent a draft specification to X/Open—who rejected it in March, after being threatened by Microsoft's assertion of intellectual property rights (IPR) over the Windows APIs

Looks like that's what it was.