Written via an interface to libfuse.
The license remains GPL because it appears that is what libfuse requires.
You will obviously need the libfuse tools and headers to build this module.
I am no expert at this but this is what I did to get this project to build on Ubuntu LTS24:
sudo apt install -y libfuse3-3 libfuse3-dev
On Fedora41:
dnf install -y fuse3 fuse3-devel
On either system:
git clone https://github.com/daveshepperd/mgwfs.git mgwfs
cd mgwfs
make
mkdir game
./mgwfs --image=<path-to-Atari-image> <path-to-local-mount-point>
Use ./mgwfs --help for list of command line options.
It has taken me quite a while to get to it, but with the enormous and grateful help of Claude 4.8, write functionality has been added. I haven't done a lot of testing with it. Claude did quite a bit of testing while it was writing its stuff, so it probably works okay. Add the --rw command line option to allow read/write to the image.
NOTE: The boot file has special marking on versions of the filesystem greater than v1.1. In order to allow you to mark a file as being a boot file, use the new tool mgwfsctl. Assuming your boot file is at relative location on the game disk somewhere/over/the/rainbow/bootme.img and you've mounted the image at /mnt/mgw, here's an example of how you would mark it as the boot file:
# Create a local mount point
mkdir -p /mnt/mgw
# Mount the Atari image on it
./mgwfs --image=<path-to-Atari-image> --rw /mnt/mgw
# [optional] If you are interested, get some info about the filesystem
./mgwfsctl stats /mnt/mgw
# Mark your file as bootable
./mgwfsctl setboot /mnt/mgw/somewhere/over/the/rainbow/bootme.img
An error will be displayed if the filesystem doesn't support the setboot option.
You are not likely to run into it in the field, but filesystems with version 1.7 allow up to 4 different boot images. Which one is booted is typically selected with a 2 position DIP switch on the game board. You would specify which boot file with an additional command line argument:
./mgwfsctl setboot /mnt/mgw/somewhere/over/the/rainbow/bootme.img 3
Would assign the boot file to last slot of the 4 available (numbered 0 through 3).
Some Atari games have a diags/checksums file. This file contains a checksum of every file on the disk, except for the index.sys, freemap.sys and any directory file. The game code looks specifically for that checksums file in that diags directory. I'm thinking it is only used when running some test selected via the selftest menus, but don't hold me to that. It's been a long time. So you can use the mgwfsctl app to build a new checksums file:
./mgwfsctl checksums /mnt/mgw/diags/checksums
Technically you could put the checksums file anywhere and name it whatever you want, but it does have to pre-exist. So, for example, if you don't already have a /mnt/mgw/foobar.cs, then:
touch /mnt/mgw/foobar.cs
./mgwfsctl checksums /mnt/mgw/foobar.cs
will put the checksums in foobar.cs, but the game code won't read it. You have to put the checksums in diags/checksums.
Note also, if the existing checksums file has a size of 0, it will checksum every file on the disk. If there is an existing checksum file, it will only (re)compute checksums on the files listed therein. You will have to use the companion project, afsys, to select which files get checksums or not (or write your own diags/checksums file and just copy it).
Good luck.