The U.S. Department of Defense, is trying to make the most of Open Source software. This is software that anyone can modify. But any software used on Department of Defense projects needs to meet security and technical standards, and can only be messed with by approved Department of Defense personnel. Typical military bureaucracy situation. The Department of Defense got around this by setting up a repository for militarily useful open source software, at a restricted access website (forge.mil). This was an analog of the original civilian, anyone is welcome, sourceforge.net site.
The Open Source concept has proved to be enormously useful. The vast majority of software professionals poking around in software are just trying to get these programs to work reliably, efficiently, and a little better. When they find a flaw, they report it. And with a lot of bug reports coming in, the software publisher will fix the damn thing quickly.
Well, not always. Software publishers make money by creating new software, not repairing the old. Microsoft, in particular, is vulnerable here. Microsoft not only produces new software, but comes out with new versions of existing product so frequently that there are always a lot of older programs still in use. The older versions are even less likely to be patched. Ironically, the two best maintained (bug free and quickly patched) bits of Internet software (Apache server software and the Linux operating system) are Open Source. In effect, no one owns them, but a coalition of users and volunteers maintain them. Sounds weird, but it works. Linux is no threat to Microsoft in the operating system area, but Apache actually has a majority of its market. Many of the open source programs are "public utility" type stuff, where many people have an interest in keeping the code working well. But many open source programs are applications that appeal to smaller audiences. Even these are kept going by small groups of volunteers.
The military found itself with lots of "open source" software early on. That's because when the first PCs appeared on the market three decades ago, many were bought by military personnel. All these early PCs had programming tools, and creating your own software was touted as a major feature. The military PCs owners proceeded to create thousands of programs that automated much work. This caused some friction with security and computer specialists, who saw this open source programming effort as undisciplined and out of control. That was an accurate assessment, but that was why this software development was so useful. The brass never were able to rein in troop efforts to develop their own software, and forge.mil is one of many efforts by the high command to encourage and channel the software development efforts by the troops.