Many of the larger open source projects receive serious backing from one or more Corporate sponsors.
Depending on CLA's and the license chosen, if contributions were made by engineers during their working hours (i.e. as part of their job) the copyright on those corporations belongs to their employers, not the individuals. The individuals might not even have the legal authority to assign the copyright via a CLA.
A similar question deals with accessing and forking the original source code. But this situation is slightly different.
In addition to complications over the copyright (perhaps another company purchases the assets of the failed one), the loss of the sponsor might also imply the loss of
- Extensive web infrastructure for hosting, distribution, and support
- A large pool of contributors who are no longer being paid to contribute
- Some large users, who perhaps had commercial support agreements, or simply lose confidence in the project once its backers depart.
So what happens to a large, popular OS project when its major corporate sponsor goes bust, taking all the above with it?