On holidays now, just a brief public uodate, along with the private response already provided by sysmocom to a related inquiry there:
The OS and. ISIM/USIM applications on the sysmocom SIM card products are proprietary by the respective CardOS vendor.
At no point did sysmocom claim those would be open source, nor could I find any publication of sysmocom or content on osmocom.org that would hint the CardOS or apps are open source software.
We of course would all wish to have open source also in card OS (and a long time ago we had some plans), but we have to pick our fights based on the available resource capacity...
Regards, Harald