
Over 11,000 people signed the petition in 2005, and a further 4,000 have now called for the software to be opened up.
IBM said in a letter to OS2World.com: "We have considered the positioning of OS/2 and open source several times in the past and, for a variety of business, technical and legal reasons, we have decided to not pursue any OS/2 open source projects.
"IBM has service offerings that continue to be available for customers who need ongoing support for OS/2, although IBM has no plans for product enhancements.
"IBM has recommended that customers on OS/2 consider migration to alternative solution offerings, and has a broad array of software assets and services to help customers migrate."
OS/2 was originally developed by Microsoft and IBM as a successor to DOS and Windows-based operating systems. Microsoft pulled out of the project after two years of development in favour of Windows 3.0.
Some at IBM have accused Microsoft of deliberately sabotaging OS/2, but the operating system was never hugely popular since it did not come preloaded on the vast majority of computers and lacked crucial device drivers for non-IBM hardware.
IBM stopped supporting the operating system in 2006, but it still has a dedicated user base and is in use today at HSBC.
The software is still for sale under the name eComStation.