This is a very tiny program (8 KB). Here is an excerpt of the original
ReadMe file (also included):

> Welcome is a simple application which allows you to edit
>  the ?Welcome to Macintosh.? message that is displayed when
>  the Mac boots.
>
> Welcome comes with no warranty, use it at your own risk.
>
> Welcome offers you a standard dialog box with the current boot
>  message and allows you to edit it. Some important points:
>  1\. You can't place special characters (e.g. tabs or returns)
>  in the text.
>  2\. The text won't be word wrapped at boot time.
>  3\. You can force the message to begin a new line by
>  placing a slash ?/? in the message. The slash won't be
>  displayed.
>
> Welcome edits the boot message from the currently open System
>  file. Some virus detection programs might complain about Welcome's
>  actions, if so you'll have to turn them off. GateKeeper and
> Disinfectant
>  Init have no problem with Welcome (i.e. there is no need to turn
> either
>  of these off before running Welcome). To edit the message on
> another
>  disk you will have to first restart with that disk.
>
> If your boot message get corrupted, you can replace it completely
>  by using ResEdit to copy the DSAT 0 resource from an original
> system
>  disk.

Compatibility
Architecture: 68k

Version 1.0 will run on System 4.2 or later, but it will display an
error message and quit if you try to run it on Mac OS 8.0 or later
Version 1.2.1 works on System 4.2-7.5.5, but not Mac OS 7.6
Attempting to run any version of Welcome on System 4.1 or earlier
causes either an ID = 03 bomb screen or an infinite loop with the
spinning-clock cursor.