The move brings the website into line with rival Facebook, which has seen strong growth since it opened up to outside programmers.
Facebook has become a portal for services such as video, audio and photos since the change.
MySpace has more than 188 million registered users, compared to the 47 million who use Facebook.
MySpace was bought by Rupert Murdoch's News Corp for $580m in 2005.
"We hoped it would do very well, but we never imagined it would do this well," Mr Murdoch told the Web 2.0 conference in San Francisco on Wednesday.
"The idea will be to allow outside developers to tightly integrate their applications into MySpace," Chris DeWolfe, the firm's chief executive, told Reuters news agency.
The social network hopes to open up the site in the next few months and hold off the challenge from Facebook.
"There's been so much excitement, energy and growth on the part of Facebook," said Forrester analyst Charlene Li. "There's a lot of pressure on MySpace to capture that energy."
Facebook already has more than 6,000 applications running on the website.
According to Nielsen Net Ratings MySpace has 78.6 million active users, versus 28.1 million on Facebook.
"I would say we're different (than Facebook) and in spite of all the hype we seem to be growing faster," Mr Murdoch told the conference.