This is part of Win16 API which allow to create versions of program from one source code to run under OS/2 and Win16. Under OS/2 program can be running under Win-OS/2 if program is Windows NE executable, and with help on Windows Libraries for OS/2, if it is OS/2 NE executable. Here is a WLO to OS/2 API mapping draft

Windows LOGO file is a raw binary with following structure

Offset	Description
0	'LOGO' signature
4	Draw logo entry point
7	Restore screen entry point

On exit of Draw logo entry point ax contains address of last required byte for restore call. All higher this address can be discarded to save memory. Format of logo data can be any (depends on Draw Logo code)