how do I run this program? I can't do it!

What is this?

Looks very suspicious - a tar wrapped in a gzip archive with an MS office doc in it....

I'm not touching that with a 10 foot pole

curl -O https://www.applefritter.com/files/apple.RX.gz

gunzip -k apple.RX.gz

# thanks to baldrick for pointing out that apple.RX is actually a "tar" file:

cp apple.RX apple.rx.tar

mkdir -p apple.rx

cd apple.rx && tar x ../apple.rx.tar

ls

Defanged.Virus  Finder.Data  Rx.GS  Rx.GS.Doc

# thankfully Rx.GS.Doc is not an MS Office .doc file.

sed 's/\r/\n/g' Rx.GS.Doc | head -n 11

.mo10  NOTE: If not printing with ProSel-16 Text Editor, remove 1st 6 lines.

.bl//Page #                        Apple-Rx                @         %       //

.ol=

.pl59

!left margin,4!

              Documentation for Apple.Rx (GS version)

              ---------------------------------------

                Copyright 1988-91 by Glen E. Bredon

# I am guessing that the starting address for Defanged.Virus is $2000.

6502 -d 2000 Defanged.Virus ff58 <(mon 60) fe2c <(mon 60) | head

                              A=AA X=00 Y=00 S=00 P=22 PC=2000  0

2000- 4C 06 22  JMP $2206     A=AA X=00 Y=00 S=00 P=22 PC=2206  3

2206- 20 58 FF  JSR $FF58     A=AA X=00 Y=00 S=FE P=22 PC=FF58  9

FF58- 60        RTS           A=AA X=00 Y=00 S=00 P=22 PC=2209  15

2209- BA        TSX           A=AA X=00 Y=00 S=00 P=22 PC=220A  17

220A- BD 00 01  LDA $0100,X   A=22 X=00 Y=00 S=00 P=20 PC=220D  21

220D- 8D 01 03  STA $0301     A=22 X=00 Y=00 S=00 P=20 PC=2210  25

2210- CA        DEX           A=22 X=FF Y=00 S=00 P=A0 PC=2211  27

2211- BD 00 01  LDA $0100,X   A=08 X=FF Y=00 S=00 P=20 PC=2214  31

2214- 8D 00 03  STA $0300     A=08 X=FF Y=00 S=00 P=20 PC=2217  35 

It's a GS/OS app. You can import the Rx.GS binary into a ProDOS disk image and set the filetype to "S16".

Screenshot:

Disk image: Apple-Rx 3.4.po.zip

Which file is missing?

If it is Finder.Data that file records the window position and size of all open windows — a feature of the Apple IIGS. I wish my Linux distro had that feature! ;)

https://www.savagetaylor.com/TIL/TIL02284.pdf