Application stacks have a long history in the proprietary software arena. Vendors such as Microsoft Corp. and Oracle Corp. have long marketed their integrated product line to customers as a way to boost interoperability and cut costs, though critics say that also leads to customers facing vendor lock-in.

In open source, most software providers remain small, offering at most a handful of applications rather than entire lineups. That put the responsibility on corporate users, or their highly paid consultants, to ensure that the software worked together -- something that could easily wipe out the savings from using free software.

The first true open-source stack emerged during the dot-com boom in the form of Web servers. Dubbed LAMP, it included the Linux operating system with the Apache HTTP Web server and MySQL database on top, supported by code written in languages such as Perl, Python or PHP. LAMP's popularity woke up vendors to the potential of packaging and testing open-source applications in a tidy way, cutting deployment time and risks for companies, especially smaller ones.

That has led to the emergence of dozens of LAMP imitators, as well as open-source software stacks running on Windows, dubbed WAMP. Critics call it a flood of poorly tested, not-very-well-integrated stacks.

"When you try to certify everything from soup to nuts, it ends up not meaning much at all," said Erik Troan, chief technology officer at rPath.