The group behind the world's most popular smartphone operating system - Symbian - is giving away "billions of dollars" worth of code for free.
The Symbian Foundation's announced that it would make its code open source in 2008 and has now completed the move.
It means that any organisation or individual can now use and modify the platform's underlying source code "for any purpose".
Symbian has shipped in more than 330m mobile phones, the foundation says.
It believes the move will attract new developers to work on the system and help speed up the pace of improvements.
"This is the largest open source migration effort ever," Lee Williams of the Symbian Foundation told BBC News.
"It will increase rate of evolution and increase the rate of innovation of the platform."
Ian Fogg, principal analyst at Forrester research, said the move was about Symbian "transitioning from one business model to another" as well as trying to gain "momentum and mindshare" for software that had been overshadowed by the release of Apple's iPhone and Google Android operating system.
Evolutionary barrier
Finnish mobile phone giant Nokia bought the software in 2008 and helped establish the non-profit Symbian Foundation to oversee its development and transition to open source.
The foundation includes Nokia, AT&T, LG, Motorola, NTT Docomo, Samsung, Sony Ericsson, STMicroelectronics, Texas Instruments and Vodafone.
The group has now released what it calls the Symbian platform as open source code. This platform unites different elements of the Symbian operating system as well as components - in particular, user interfaces - developed by individual members.
Until now, Symbian's source code was only open to members of the organisation.
It can be downloaded from the foundation's website from 1400 GMT
