Cloning with --recursive parameter not possible

[classiccoding]

$ git clone --recursive https://github.com/freem/freemlib-neogeo
Cloning into 'freemlib-neogeo'...
remote: Counting objects: 3298, done.
remote: Total 3298 (delta 0), reused 0 (delta 0), pack-reused 3298
Receiving objects: 100% (3298/3298), 846.65 KiB | 85.00 KiB/s, done.
Resolving deltas: 100% (2337/2337), done.
Checking connectivity... done.
Submodule 'tools/adpcma' ([email protected]:freem/adpcma.git) registered for path 'tools/adpcma'
Submodule 'tools/romwak' ([email protected]:freem/romwak.git) registered for path 'tools/romwak'
Cloning into '[...]/freemlib-neogeo/tools/adpcma'...
Permission denied (publickey).
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.
fatal: clone of '[email protected]:freem/adpcma.git' into submodule path '[...]/freemlib-neogeo/tools/adpcma' failed