The two-disc DVD set, intended to offer 1,000 activities and help non-specialists to teach Latin, should have been ready by May 2002.
An attempt to release the discs last year failed as schools testing them could not make them work, said a source close to the project.
The discs still contain thousands of errors, will not work with Apple Macintosh computers and have no index for the activities.
Supporters of Latin in schools now fear that the software may never appear.
At 50 schools involved in the pilot project, the number of pupils continuing to GCSE-level more than doubled.
It was hoped that the software might generate similar enthusiasm in schools in which Latin is not on offer at present.
Will Griffiths, director of the Cambridge Schools Latin Project, said:
"There is no other solid programme to make Latin more accessible. This had genuine potential to make a change."
Just 15,593 students took classics subjects at GCSE last year.
The AQA exam board angered classicists last year by announcing that it would axe the subject at GCSE from 2006.
The Department for Education and Skills and Granada Learning, which is responsible for the software, said the project was in an "advanced state of testing" and would be available soon.