WinFsp is an open-source project hosted at GitHub. There is also a mirror at BitBucket. You can access and download its source code from both of these locations:
WinFsp is available under the GPLv3 license. If you find the constraints of the GPLv3 too onerous, a commercial license is also available. Please contact Bill Zissimopoulos <billziss at navimatics.com> for more details.
Contributors to WinFsp MUST accept the WinFsp Contributor Agreement. The agreement gives the original author (Bill Zissimopoulos <billziss at navimatics.com>) and the contributor joint copyright interests in the contributed code. Please read the file doc/Contributors.txt in the source distribution for more details.