There have been many analyses of Skype’s behaviour over the years (the most famous perhaps is from Baset and Schultzrinne), but as far as Vulture Central is aware, nobody has yet gone so far as to reverse-engineer the whole kit-and-caboodle.
That’s the claim being made by Efim Bushmanov on this blog, where he offers his reverse-engineered Skype source code available for download.
His work is almost certain to spark debate over the legality – and license-compliance – of reverse-engineering the software. It’s also quite likely to spark a response from Skype’s new owner, Microsoft.
The Register has not yet had the time to install or test the code (if that were, in fact, legal to do), so we can’t vouch for its operation.
Whether Bushmanov has broken any laws or breached any license terms depends on the conditions under which he’s undertaken the project (and to some extent, the jurisdiction in which he worked).
It’s hard to replicate perfectly the behaviour of any software under completely clean-room conditions, and probably even harder to prove that such conditions existed. Bushmanov would at the very least have to demonstrate that he worked without a copy of the software to hand – that somebody else ran the software and observed its behaviours. The authors of the reverse-engineered copy would have to write their software solely from Skype’s reported behaviour under different conditions.
According to this discussion on Hacker News, Bushmanov seems to be including original Skype binaries in its downloads, which would be a no-no. However, HN’s interpretation is based on the filenames rather than the contents of the files; perhaps Bushmanov simply didn’t have the nous to give his files names that weren’t subject to confusion.
The Register does however anticipate a swift response from Microsoft, if the software is what it claims to be. ®