HN user
I'd be very surprised if Broadcom released the source code for their firmware. It would probably have to be a complete rewrite from reverse engineered specifications, like the original IBM PC BIOS was cloned. Except a lot more difficult as these firmwares are comparatively huge.
I think they're all dependencies shared by many other Windows components, and will probably mostly be the versioned API Sets rather than specifically named DLLs. But if there is anything Paint-specific it could just be copied over too.
The Raspberry Pi isn't open source. Broadcom only releases their firmware as binaries.
If you need regular restarts of SQL Server then there's something really quite wrong with your setup.
Disappointing comments in this thread. Lots of worthless complaining, and scant technical talk on solutions to this barely significant 'problem'.
If you want to keep the original mspaint.exe and don't want to use the Store for some reason, you can literally just copy it from any Windows 10 install media prior to RS3. Or from a running system. It's not difficult.