There's a link in my profile to the company products page for my group, which includes a link to the STOP OS page. There used to be additional documents you could download from those pages, but it looks like they're not working any more.
The short version is that it implements three different MAC (mandatory access control) policies (RBAC, Bell-LaPadula, Biba) and the standard *nix DAC policies. It's designed for safely handling/moving data on/between multiple classification levels. (See the SCOMP section in [0] for history). From a user perspective, it's very similar to Linux, with a largely Linux-like ABI and similar user interfaces, including a full X/xfce GUI environment if you want, though most actual deployments tend to run headless with only required software loaded. It runs on both small embedded boards and large enterprise servers and a bunch in between.
The data diode one reminds me of a null-modem cable I once did where I forked the TX line to a second DB-25 so that a server could eavesdrop the data coming from the PABX to the call tracking box. The server would then push it to all stations connected to a socket, where a Java applet would display the proper greeting the support agent would use when the call came in.
The short version is that it implements three different MAC (mandatory access control) policies (RBAC, Bell-LaPadula, Biba) and the standard *nix DAC policies. It's designed for safely handling/moving data on/between multiple classification levels. (See the SCOMP section in [0] for history). From a user perspective, it's very similar to Linux, with a largely Linux-like ABI and similar user interfaces, including a full X/xfce GUI environment if you want, though most actual deployments tend to run headless with only required software loaded. It runs on both small embedded boards and large enterprise servers and a bunch in between.
[0] https://multicians.org/b2.html