Identi.ca’s plans to build an open-source alternative to Twitter got a vote of confidence this week with an investment from the VCs at Montreal Start Up. While the amount of the financing wasn’t disclosed, Montreal Start Up Managing Partner John Stokes said the firm invests between C$150,000 ($120,135) and C$400,000 ($320,329) per deal.

A bigger question is why microblogging companies are getting any investment at all. If Twitter can’t find revenues with the vast majority of market share, why would an open-source version make money? Identi.ca founder and CEO Evan Prodromou says open source gives the company “commercialization options that Twitter doesn’t [have].” For example the company can charge a fee for public or private implementations, or be the basis for microblogs on other web sites.

Identi.ca has some other tricks up its sleeve, too. Their APIs are Twitter-compatible, so they should work with third-party features like search, hashtags and analytics. And it’s a federated model: You can run an identi.ca instance privately, or share messages with other id