You could call them the "Little 4," a play on the "Big 4" systems management companies: BMC, CA Technologies, HP, and IBM.
The Little 4 may be smaller in terms of their bottom lines, but in terms of systems management capabilities, there's nothing little about the open source offerings from Zenoss, Hyperic, GroundWork Open Source, and The OpenNMS Group.
This is a biosphere within the open source ecosystem that has seen a lot of flux in the past few years. In 2006, Zenoss was one of six vendors (the others being Ayamon, Emu Software, Qlusters, Symbiot, and Webmin) that launched the Open Management Consortium (OMC), "an effort to promote the adoption, development, and integration of systems and network management software based on open source and open standards technologies."
Now, the OMC is long gone, faded into the mists of oblivion, while other firms and technologies have stepped up to fill the systems management sector, which encompasses monitoring, systems, and network management tools -- and generates about $4 billion in sales. It is projected that this will eventually expand to around $12-$14 billion in annual sales, with just four companies taking up to half of those sales numbers.
There is not much linking these companies together, other than a very healthy sense of coopetition. For the most part, the atmosphere in systems management land is friendly, though there are some skirmishes every once in a while.
Read the rest at Enterprise Networking Planet.