Based on the source code released by Sophos

This release is built from the original sources as released by Sophos, using VS2015. The only modification made is a repaired encoding in SbieControl.rc

The SbieDrv.sys driver must be signed, and since the appropriate certificates are prohibitively expensive, I had to use a leaked code signing certificate I found laying around the Internet.
This means some anti-malware applications flag it as potentially dangerous: https://www.virustotal.com/gui/file/f1587c91eb6ff49c20fa1f026358ebe8f9bc10625f86013c975abe894cd146ac/detection

Note: For Windows XP, use SandboxieInstall32_xp.exe