Just like how Android is open source, the ROMs created for Android devices in general are open source too, allowing developers not on the team of that particular ROM to develop and tweak it to their needs. Unfortunately these ROMs might not be the most stable and the quality isn’t always guaranteed, which is exactly how the folks at Team CyanogenMod feels. The group of developers posted on their blog that they will be rolling out a new M-series of ROMs for CyanogenMod 10 (which is based off Android 4.1 Jelly Bean, for those wondering).
These ROMs will be released on a monthly basis at the start of every month and are supposedly more “stable” builds whose quality is consistent with that of Team CyanogenMod’s releases. So if you were relying on third-party developers outside of the team, we guess this is good news for you. So far a list of supported devices has been listed, so head on over to their blog for the details and to see if your device is on the list.