The app was launched last Saturday by Dr Janil Puthucheary, senior minister of state at Singapore's Ministry of Communications and Information.
In a statement on Facebook, Foreign Minister Vivian Balakrishnan said on Monday that the source code for the app, which has been developed by the Government Technology Agency (GovTech) and the Ministry of Health, would be made freely available.
Dr Balakrishnan, who is also the Minister-in-charge of the Smart Nation Initiative, said: "We believe that making our code available to the world will enhance trust and collaboration in dealing with a global threat that does not respect boundaries, political systems or economies. Together, we can make our world safer for everyone."
Courtesy Government Technology Agency, Singapore
Jason Bay, senior director of Government Digital Services at GovTech and leader of the team that developed TraceTogether, said in a post about the app that Bluetooth had been used because GPS, while good in open spaces, fared poorly when it came to indoor and urbanised settings.
In Singapore, people live mostly in apartments. Said Bay: "If you are one floor down in a building, your GPS location could look the same as someone in the floor above you because of signal reflections and multipath propagation effects."
He said the use of GPS would also raise privacy and data security concerns and if users were reluctant to use the app because of such concerns, its efficacy would be greatly hampered.
“So instead of attempting to tackle the issue of contact tracing by answering the question of ‘where,’ we address contact tracing by answering the question of ‘who’,” Bay explained.
“After all, you could argue that the virus doesn’t care where transmission happens; it’s only interested in whether there is a hospitable host in close contact.”
TraceTogether only needed Location Permissions to know the relative distance between users and it did does not collect or use any real-world geographic location, he added.